Fine needle aspiration (FNA) is accepted as a first line of investigation in any patient with a mass lesion. Superficial lesions can be aspirated by palpation; radiological imaging (ie. ultrasound, fluoroscopy, and computerised tomography) can guide fine needles to deeply located lesions. In common with many cytopathological investigations, the procedure can be quick, inexpensive and reliable. It requires easily available equipment, takes very little time to perform, causes minimal trauma, and can be repeated as often as required. As an investigative technique it is acceptable to most patients and it rapidly provides a diagnosis on which to base further management.
The provision of comprehensive FNA services should be under the direction of a named Cellular Pathologist with responsibility for overseeing FNA services, usually the Head of Cytopathology Services. In large departments the responsibility may be delegated to other cytopathologits.
The responsibility for taking FNAs should lie in the hands of individuals who have a sufficient FNA workload to gain and maintain the necessary expertise and who are subject to clinical audit. In many centres cytopathologists take specimens directly from patients with palpable lesions. There are three levels of skill required in providing a safe and reliable FNA service; taking the sample, preparing it, and interpreting the findings. The interpretation is made in the context of the clinical findings and the results of other investigations; it is dependent on obtaining adequate samples and preparing them to maximise their diagnostically relevant information. Appropriately trained cytopathologists should be able to acquire all these skills, and it is they who are best placed to provide a comprehensive service (Refs 1-25). Deep-seated lesions in which ultrasound or radiological guidance is required to target the lesion are better suited to aspiration by appropriately trained radiologists.
Trained biomedical scientists should be available to support clinical staff taking FNAs, by collecting the samples in appropriate media and preparing direct smears as required. Immediate assessment of specimen adequacy may be carried out by cytopathologists or by suitably trained and experienced biomedical scientists under the guidance of cytopathologists. In addition to assessing specimen adequacy, it may be possible for cytoipathologists to give a provisional diagnosis, in which case the diagnosis should be recorded verbatim at the time it was given and included in the text of the final report in the same way a frozen section is reported in surgical pathology (see below).
In many institutions FNAs are taken by a variety of non-cytopathology staff, including surgeons, physicians, specialist nurses and appropriately trained radiographers. Providing the aspirator is well trained, has sufficient practice to maintain his or her skills, has a close working relationship with the pathology department and is subject to clinical audit, there should be no difficulty in achieving a high quality service (Ref 26,27).
Fine needle aspirates should not be taken by unsupervised staff who have no training in the technique, or by staff who do not take FNAs on a regular basis.
When introducing comprehensive FNA services to a hospital setting previously lacking such a service, cytopathologists usually start by offering to take FNAs in a variety of out-patients� clinics, wards and pre- or intra-operatively in operating theatres. As the service becomes more widely used, alternative means of service provision is often necessary.
A common solution is to hold one or more FNA sessions in the hospital Out-Patient Department. These may be run in association with existing clinics (e.g. Breast Clinics, Head & Neck Clinics, etc), or run in their own right by cytopathology staff. The Out-Patient Department has the considerable advantage of easy access for patients and support by dedicated nursing and reception staff. However, the clinic space will have several users and equipment must be moved before and after each session; it is also difficult to extend the number of sessions when the service becomes overstretched by its own success.
The ideal solution for a busy FNA service is to set up a dedicated, purpose-built FNA Clinic that can be operated according to a set schedule. This must have close links with Cellular Pathology, and some services have a dedicated FNA Clinic located within the Cytopathology Laboratory. In the absence of nursing and administrative staff, the laboratory staff working in the clinic must be trained to deal appropriately with patients and should be trained in basic life support techniques. The clinic should always be attended by a suitably trained, medically qualified cytopathologist. The clinic should be managed according to Trust protocols for other out-patient clinics and have waiting areas (suitable for adults and children) with toilets and fresh drinking water. Access to the FNA Clinic and its facilities should be provided for disabled people.
Given the need for patient access, and the limited availability and suitability of laboratory space in many units, it may be better to site FNA clinics in an Out-Patient Clinic. A location nearby, or even within the Radiology Department is a good alternative, especially if a large volume of image guided FNAs are done. FNA clinics are well suited to the concept of ambulatory care in a polyclinic setting, where out-patients can be seen and investigated by as many specialists as necessary during a single visit to the hospital.
In services that lack a dedicated FNA Clinic, where FNAs are limited to an ad hoc, on-demand service to variety of clinics there will be a significant additional journey time from the laboratory to the clinic and back again; this must be included as part of the workload. With a dedicated FNA Clinic the service is more time-efficient and can handle a larger volume of FNA work. Each FNA consultation is likely to take between 10 and 20 minutes. The time-frame for the consultation should allow time for explaining the procedure to the patient, examining the patient, taking the FNA, immediate staining and microscopic assessment for sample adequacy, repeating aspirates when necessary and �rapid reporting�. Trust guidelines for obtaining consent should be followed.
Cytopathologists should use their clinical judgment to determine if a referred patient has a suitable target for FNA or not. They should not attempt to take FNAs if they consider the request to be clinically inappropriate or if the lesion is not palpable; they should suggest referral for radiological guidance in cases where they consider this to be appropriate.
Aspiration is followed by a formal reporting session by the consultant in the laboratory, including all cases where a provisional rapid result has been given. Every FNA clinic therefore attracts the minimum of two DPAs (Direct Patient Activities) according to the 2003 Consultant Contract document (Ref 29). Workload should be carefully monitored, to include the number of slides/case and balanced by available resources (Ref 30). The need for increased resources should be identified before an increase in workload is undertaken.
Many departments fail, initially at least, to appreciate the amount of work involved in establishing a quality FNA service. Cytopathologists must have sufficient time away from the clinic to carry out their more traditional tasks of reporting cervical smears and exfoliative cytopathology specimens, and participating in teaching, audit, research and management. Most will want to maintain an active interest in surgical pathology and autopsy services; staffing levels should ensure that these duties, and absences during times of annual and professional leave, do not cause a hiatus in the FNA service.
FNA clinics lend themselves to referrals from community physicians and general dental and medical practitioners. Provided the referral pathways to GPs are clearly in place, establishing diagnoses in a primary care setting can have a positive effect on hospital referral practice, with patients being sent to the appropriate specialists for specific investigation and treatment rather than for preliminary work-up.
Much of the cytopathologist's time is spent with Primary Care and Out-Patient referrals, however, a cytopathology team should be available to visit hospitalised in-patients and, potentially also, bed-bound patients within the community. While the equipment needed to take a bedside FNA is light and easily portable it is important to maintain health and safety precautions at all times away from the clinic.
The equipment needed for a high quality FNA service is generally inexpensive and readily available.
Needle gauge is based on external diameter. Fine needle should be 23 gauge (external diameter 0.6mm) or less. In exceptional cases a 22 gauge needle can be used (external diameter 0.7 mm). This is important for the following reasons: a) it is less painful. b) it causes less bleeding c) the risk of tumour cell seeding is dramatically reduced. Thicker needles (G18, external diameter 1.2mm, or wider) carry an ever-increasing risk of complications including significant haemorrhage. Virtually all reports of tumour-spread by needle tract seeding are in patients aspirated by needles that were either not fine or had irregular surfaces capable of dragging cells around their periphery as they were withdrawn.
To be suitable for FNA, needles should have a long bevel with a large circumference at their cutting edge. Most disposable venepuncture needles and spinal needles are suitable for FNA. Longer fine needles are required for deeply sited lesions targeted by image guidance. These needles should have a stylet; several different tissues will be traversed before the needle tip reaches its target (eg. subcutis, serosa, non-involved viscera, blood vessels, etc) and the stylet prevents the needle sampling tissues en route and filling with blood clot or non-lesional tissue before the target is reached. Without a stylet a long needle may be uncontrollably, and dangerously, flexible. Variable length spinal needles (G22 or finer) are suitable but several specialist needles are also available.
For some deep site aspirates an outer co-axial needle is used to target the lesion then finer needles are inserted within its lumen to repeatedly sample the mass. In transthoracic FNAs this permits multiple passes with only a single puncture of the pleura, thus minimizing the risk of significant pneumothorax. It also minimizes the potential for tumour cells to seed along the needle tract.
For palpable lesions both a syringe and a syringe holder may be used, although the free-needle technique, described below, is for many aspirators the preferred technique for many palpable lumps. If used, the syringe holder frees one hand to stretch the overlying skin and immobilise the lump, and minimises the effort needed to create sufficient negative pressure. The Swedish-designed Cameco syringe holder is ideal, though alternatives are now available. Either a 10ml or a 20 ml sterile disposable plastic syringe can be used, depending on personal preference. A Vacutainer needle and collection bottle are of no value in FNA practice, as the negative pressure cannot be controlled during the procedure.
Clean slides with frosted ends are required if direct smears are to be prepared at the time an aspirate is taken. Direct smears can be either wet-fixed by alcohol spray or (preferably) by immersion, or air-dried. The latter, while unfixed, are potentially biohazardous and should be handled accordingly.
Needle washings taken in transport media provide additional material for cytopathological study. In some centres a liquid-based approach has replaced direct smears with the entire specimen being washed into transport media. This precludes rapid assessment of specimen adequacy and is not recommended unless resources are so limited that there is no laboratory support for attending FNAs.
There are two main types of transport media; fixation fluid that obviously kills the cells, and non-fixative/culture fluid that will keep the cells alive until they can be processed. If only fixed cell preparations are required then a Saccomano-type fixative is satisfactory. If only cell blocks are to be prepared then 10% buffered formalin is satisfactory. Fixation precludes the subsequent preparation of properly air-dried material but keeps the process technically simple. Keeping cells alive maximises the information that can be gained from them providing they are handled appropriately and in a timely fashion. Roswell Park Memorial Institute (RPMI) 1640 cell culture medium kept at 40c gives good results; this includes 10% fetal calf serum, 1% penicillin-streptomycin solution and a small amount of heparin. Cells taken into RPMI 1640 medium will survive between 12 to 72 hours at 4c. Hanks� physiological saline, which lacks antimicrobial agents, is perhaps a more appropriate media as it is suitable for samples requiring microbiological investigation. Sterile normal saline, which is universally available in the hospital environment, can also be used for transporting samples, providing processing is not unduly delayed.
The FNA kit should include several 20ml universal containers pre-filled with transport media. If Hank�s or RPMI 1640 is being used make sure it is fresh (the pH indicator included in the fluid gives it a red colour when fresh; a change in colour to purple indicates contamination by bacteria or fungi). After drawing the transport fluid into the syringe containing the cellular material the needle should be removed before it is expressed to avoid damage to cells, which may be caused by forceful expulsion at high pressure through a narrow gauge needle.
Cells in Hank�s (and normal) saline can be used for Microbiological investigations, for flow cytometry and immunosuspension studies, and for molecular pathology investigations, in addition to being further processed for traditional microscopic assessment via cell blocks, direct smears or cytocentrifugation or other LBC methods (see Appendices).
Because all fresh body fluids may harbour unexpected biohazards, such as Mycobacteria or hepatitis B virus, it is essential that suitable gloves are worn during aspiration and slide preparation. Surgical gloves of the correct size are most suitable. Latex-free gloves should be available for sensitised staff or patients. In high-risk cases masks, eye protection and an apron or gown may be appropriate. Patients with active infections should themselves wear masks. There are no absolute contra-indications to making direct smears, which are essential for rapid assessment, but appropriate care must be taken to minimise risk.
Careful needle disposal, avoiding re-sheathing, should be carried out and staff should be aware of local arrangements for needle stick injuries. Written protocols should be available for dealing with needle stick injuries at all sites where FNAs are carried out. Medical and non-medical staff should receive instructions for management of such injuries, including guidelines for requesting blood tests from patients under some circumstances, as part of their training and induction for working in FNA clinics.
Local anaesthesia of the overlying skin and proposed needle tract is only needed in especially sensitive locations (eg. nipple, lip, eyelid), for small children or in situations where multiple passes of the needle are planned (eg. FNAs of large masses, or during deep-site aspirations) but for most palpable sites it is not required. When local anaesthetic is wanted a very fine needle (G25 or finer) should be used to infiltrate both skin and proposed needle track; some practitioners advocate the use of dental local anaesthetic equipment, with 30G needles and easily held metal syringes. A small volume of 2% lignocaine is generally sufficient. Application of anaesthetic cream (eg EMLA cream) to the proposed puncture site according to the manufacturer�s instructions, before doing the FNA is helpful in children and needle-phobic patients. Ethylene spray for skin anaesthesia can also be used. However, its effect is only a little greater than placebo
Other than a patient refusing informed consent there are no absolute contraindications to FNA of superficial masses. There are specific contraindications to deep site aspirates and these depend to some extent on site.
Anticoagulant therapy and intrinsic bleeding problems increase the risk of bruising and haemorrhage; while this can be controlled by applying pressure to superficial targets, deep site aspirates should only be performed after the bleeding abnormality is corrected.
Intractable cough and poor respiratory function are absolute contraindications to transthoracic FNA. Some degree of pneumothorax is almost inevitable when even the finest of needles breach the pleura; while this only occasionally requires treatment even a minor pneumothorax in a respiratory cripple carries a significant risk of mortality.
Aspirates of unsuspected Hydatid cysts have been reported without serious consequences but the potential risk of anaphylactic shock resulting from rupture is well known and they are best avoided.
FNA of carotid body tumours may cause catecholamine release with the potential risk of hypertensive crisis; for this reason suspected carotid body tumours should not be aspirated. However, it is impossible to practice FNA cytology in the Head and Neck Clinic and not occasionally aspirate an unsuspected carotid body tumour. There are no reports of adverse reactions to FNA in the cytology literature.
A request form should be completed by the referring clinician in all cases where FNA is requested. Additional clinical information can be added if the cytopathologist has direct contact with the patient but this should not replace the referring clinician's responsibility in completing the request form.
The technique of FNA has a clear purpose as well as certain limitations and complications; it is important that these are discussed honestly and fully with the patient before he or she is asked to consent to aspiration. At least verbal consent should be sought in all cases; some Trusts now require patients to sign a written consent form. Information leaflets are helpful in answering patients� questions in advance of the FNA appointment (an example is given in Appendix E).
Successful FNA technique is best learnt during an apprenticeship with an experienced Cytopathologist. The following approach to taking FNAs and the method will not suit every practitioner; it is intended as guidance rather than proscription.
The aspirator should put the patient at ease before taking as full a history as necessary. The technique of FNA should be briefly explained, emphasising the purpose of the test, its limitations, its potential complications and the often necessary need to repeat the aspiration to obtain an adequate sample or additional material for ancillary tests. Occasional patients complain of bruising and discomfort the day after aspiration and patients should be warned about this and advised of the suitability of non-aspirin pain relief, as aspirin can increase bruising. Ask the patient if he or she has any questions or particular concerns before obtaining their consent to proceed.
The patient should be asked to undress as appropriate and to get on the examination couch. It is best not to try to aspirate patients sitting in an ordinary chair as they can move or faint quite unexpectedly; special chairs with head rests are suitable for some but not all situations. An assistant should be present at all times to act as chaperone for the patient, and as an assistant to the aspirator. This assistant should know what to expect and be trained accordingly; they can be a nurse, a biomedical scientist, an MLA or doctor.
The aspirator should then examine the patient as fully as necessary to determine if FNA is appropriate and to consider where the needle should be placed, and how many aspirates and what preparations are likely to be useful. It should be possible to determine the location, size, shape, consistency and mobility of the target by careful palpation. When the aspirator has a good idea of what is needed, slides should be laid out ready for direct smears, and containers of fixative and transport media should be made ready on a designated preparation area. Slides should be labelled prior to the procedure, including the slide used for spreading. Then both the aspirator and the assistant should put on a pair of disposable gloves before returning to the patient.
The skin, or mucosal surface, over the lesion should be cleaned with an alcohol wipe. If local anaesthetic is to be used, it takes at least two minutes to achieve its full numbing effect. If required, the FNA gun (needle, syringe and holder) can be assembled during this time. When ready, one hand should be used to feel and steady the lump; the other hand is free to hold and manipulate the FNA gun or the free needle.
It is worth remembering that many tumours have necrotic centres and diagnostic material may only be found at the periphery of the mass. Multiple samples may be obtained by FNA. This reduces sample error and helps to obtain sufficient material for ancillary tests, the need for which may be guided by rapidly staining and examining one of the direct smears (see below). For larger lesions it is possible to use a single anaesthetised skin site for repeated aspiration, riding the anaesthetised skin over the lump to gain several separate entry points into the mass, producing additional sampling while minimising patient discomfort.
The FNA gun is held in one hand; the thumb and first two fingers of the free hand can be used to stretch the skin over the lesion and to act like a bridge for the syringe as if it were snooker or pool cue. The needle should be pushed quickly through the skin at right angles to it and immediately on into the lump. The syringe may then be drawn back using the holder to create negative pressure as required. Cells are scraped by the cutting edge at the tip of the needle as it is pushed repeatedly through the lesion. A rotating or screwing action of the forearm is helpful as this helps the needle to core through the tissue. Negative pressure from the FNA gun helps to hold tissues against the needles cutting edge, and this may improve the cell yield, especially from tumours that have a prominent stromal component (e.g. schirrous breast carcinomas). The needle tip is moved back and forth and the needle is angled to sample different areas of the lesion without removing the needle from the skin.
After a few passes, or as soon as material is seen in the hub of the needle, the negative pressure is released and the needle, along with its sample, is withdrawn. If negative pressure is not released before the needle is withdrawn the sample will be sucked violently from the needle along with air into the syringe; this has the effect of traumatising cells and limits the material available for preparation of direct smears. Use of an extension tube, rather than attaching the needle to a syringe directly, can be helpful in locations where a syringe holder would be difficult or frightening for the patient (eg. near the eyes), but an assistant is then necessary in order to apply suction to the syringe.
Zajdela described the use of a fine needle without a syringe (ref 7); a modification of this technique, using an attached 2ml syringe without a holder and without applying negative pressure, may be used to similar effect. The needle is held between forefinger and thumb and passed through the skin directly into the lesion. The needle is rotated while in the lesion to capture cells more by capillary action than by cutting action at the needle�s tip. Although cell yield may be reduced, this technique can be helpful in aspirating vascular tissues (eg. thyroid) to limit bleeding, or in lymphoid tissues, where cells generally lack desmosomal or other tissue restraints. Although the cell yield per pass is generally lower than when suction is applied, this technique has distinct advantages. The aspirator has more control over the needle, allowing for a more vigorous manipulation using the thumb and forefinger, than is possible with the syringe holder, as the latter necessitates a forearm movement. The procedure is generally less painful and the patient is saved the undue anxiety experienced when facing an FNA gun. As the patient is more relaxed there is less difficulty in obtaining assent for repeated passes, thus negating the disadvantage of a small sample.
As soon as the needle is withdrawn the aspirator or assistant should press carefully and firmly against the aspiration site for about a minute to reduce bruising; gently holding a sterile gauze or cotton wool against the skin is not enough. Failure to apply suitable pressure can lead to the formation of sizeable haematomas. It is not good practice to expect patients to press for themselves. A plaster may be applied once haemostasis is achieved; remember to check if the patient is allergic before using an elastic-containing plaster.
With the aspirator or assistant pressing on the aspiration site, the other is free to prepare the sample ready for transport to the laboratory. This needs to be done carefully in order to maintain safety and to make best use of the cells obtained.
The type of preparation depends on the clinical situation, the information required and the resources available.
If the slides are to be prepared by the assistant rather than the person performing the aspirate, the apparatus must be handed over with the needle pointing away from the assistant. Otherwise, especially if a syringe is not used, the needle should be placed in a small tray.
Direct smears permit rapid staining and assessment at the time an aspirate is taken and are very helpful in reducing the number of unsatisfactory FNAs. They are the mainstay of immediate diagnosis �one-stop� FNA clinics. While direct smears may be used for some ancillary tests, their number is usually limited and a properly handled needle rinse offers a more appropriate source of diagnostic material.
After aspiration the needle is removed from the syringe, air is drawn into the latter and the needle is re-attached. Taking great care to minimise spray, a small amount of material is delivered onto a glass slide a third of the way from its frosted end. A single slide may be used to pick up material and used to transfer this in small aliquots onto several slides for spreading. The spreading slide is placed on the specimen slide with one edge resting well below the material to act as a pivot; its free edge is brought gently down to just touch the wet material and at the same time this spreading slide is moved quickly back to spread the material by capillary (not dragging or crushing) action. In this way the cellular content of the material is subjected to minimum trauma. With practice a single aspirate can yield sufficient material to produce many direct smears. However, if needle rinses are used it is recommended that the majority of the sample is committed to fluid, limiting the direct smears to one wet-fixed and one air-dried.
In very bloody aspirates a spreading slide can be used to separate fluid blood from more solid fragments of tissue; holding the slide at a slight angle allows blood to drain away from the cellular material, which can then be picked up by a second spreading slide and directly smeared onto additional slides. Heavily blood-stained aspirates are best committed to the needle rinse fluid for processing (ie. to separate blood from diagnostically useful cells; see Appendix A) back in the laboratory.
The patient's identity should be written in pencil on the frosted end of all prepared slides. This should be done prior to procedure. Ideally both Papanicolau and Giemsa stained slides should be available for microscopy. Providing there is sufficient material, at least one slide should be wet-fixed by spraying or immersion in 99% ethanol or its equivalent; the rest should be spread rather more thinly to facilitate rapid air-drying. Holding a slide still with its back against the warmth of a (gloved) hand, near a light bulb or on a small warming plate facilitates rapid (and safe) air-drying.
All unused slides prepared for the procedure, including the spreader if this is not needed, should be discarded.
Needle rinses are especially useful for ancillary tests, such as special stains, immunostaining, microbiological investigations, flow cytometry or molecular testing. Needle rinses may be heavily bloodstained and include necrotic debris as well as viable cells of diagnostic interest. Needle rinses taken into normal saline or other transport media can be manipulated in the laboratory to produce slides free of blood and debris using centrifugation with gradient gels; alternatively cell blocks may be prepared (see Appendix A)
One or more air-dried direct smears may be post-fixed by immersion in 100% methanol and rapidly stained using a water-based Romanowsky method (eg. Diff-Quik) for immediate microscopic examination (remember to remove your gloves before touching the microscope). This enables immediate recognition of inadequate aspirates and appropriate repeat sampling. If a diagnosis is possible on the rapidly stained smears then no further material is taken. A further aspirate may be taken if ancillary testing is considered necessary, with all subsequent material being washed directly into fixative or transport medium as required. For example, if an infection is considered likely then a separate aspirate may be taken and washed into sterile normal saline for microbiological investigation.
There is an increasing demand for rapid diagnoses, and it is possible to offer a rapid diagnosis using quick staining techniques such as Diff Quik (on air dried) or toluidine blue (on alcohol fixed smears). Papanicoloau or H&E stains may also be used in a rapid setting but these take a little longer to prepare. There are potential pitfalls in offering such a service. All members of the team, including the cytopathologist and the requesting clinician, must know the limitations of rapid stains and be prepared to await routine preparations in difficult cases. While a positive diagnosis of malignancy may be secured on a single slide the reverse is not true; a negative report can only be issued after all the material has been examined. It is important that standards are not compromised in order to achieve rapid reporting. It should always be possible to defer the final report in difficult cases. If it is laboratory practice to prepare both Papanicolaou and Romanovsky stained slides for routine reporting then these should both be made available for rapid reporting. Clinical demands for rapid reporting must not be detrimental the quality and reliability of the service.
The preliminary, verbal report to clinicians, made on a rapidly processed slides from an FNA should be recorded verbatim in the final report, as is done for frozen sections in surgical pathology practice. Any discrepancies between the two reports should be noted and explained (if possible) in the final report.
The provision of a rapid, �one-stop� FNA service has obvious workload implications, as mentioned above in the �Workload� section.
Radiologists will carry out most image-guided FNAs themselves, using their own guidelines. The following guidelines are designed to inform pathologists and biomedical scientists attending the sessions where aspirates are taken, but should be made available to radiologists and discussed with them, especially when combined radiology/pathology FNA sessions are set up. In some instances, cytopathologists may be trained to take FNAs with ultrasound guidance under the direction of a radiologist.
Lesions may be located anywhere within the body but most can be sampled with fine needles providing they are visible with one of the many imaging techniques now available. The choice of imaging modality depends on the lesion size and location. Fine needles can pass through most organs without causing significant damage, permitting the safe sampling of most lesions. In all cases the shortest distance to the target should be selected unless bones (eg. ribs) or vital organs are in the way. Occasionally the surgical approach may influence the FNA approach in order that the track is excised although the seeding of an FNA track is extremely uncommon. The radiologist should obtain informed consent. Deep-site FNAs require a sterile operating field.
Close cooperation between radiological and cytopathological teams is essential for a high quality image-guided FNA service. It is very helpful to have an experienced cytopathologist on-site to prepare and rapidly examine aspirates. A mobile minilab, complete with slides, stains and other consumables, together with a quality microscope, is easy to maintain in the Radiology Department and provides an excellent forum for teaching as well as reporting. Health and safety precautions should be observed at all times, and are particularly important in thoracic aspirates where there should be a high index of suspicion for mycobaterial infection in mass lesions
This is may be useful even when abnormalities are palpable as it can be used to ensure that the target has been appropriately sampled and that vital structures (eg. the carotid artery) are avoided. Ultrasound (US) is readily available and, in contrast to computed tomography (CT) guided procedures, provides a rapid, safe and inexpensive means of guiding FNAs
It is important to remind radiologists to wipe off the gel from the puncture site as it can produce fixation artefacts in the specimen preparations. The gel can be wiped off carefully with a swab, but a no-touch technique with both hands behind the needle is essential to avoid the risk of needle-stick injury if this is done. During aspiration sonographic contact can also be provided by sterile water or skin disinfectant without the need for gel.
In some situations, especially in the head and neck it may be technically difficult to have an ultrasound transducer on the skin and to needle the lesion at the same time, because of space/anatomical reasons. Even then, ultrasound confirmation of the lesion, and particularly measuring its depth from the skin surface can be very helpful. Visualisation of the needle tip is one of the most important skills to master. Special needles with increased echogenicity are available; these are more easily seen but are not essential. Scanning is usually performed in a plane allowing some obliquity to the anticipated track in order to facilitate needle visualisation. Gentle back and forth movement of the needle as it advances toward the target produces movement and distortion of tissues at the needle tip improving conspicuity. A hardcopy image of the needle in correct position within the lesion is helpful documentation of the procedure.
For superficial targets a 3cm long 23 G venepuncture needle is usually suitable. For deeper targets it is best to use a 22 G spinal needle complete with stylet. As soon as the needle is in the target its stylet is removed, a syringe is attached and negative pressure applied as the needle is moved rapidly back and forth within the mass. Negative pressure is not always required and is best avoided in vascular lesions (eg. of the thyroid gland) where capillary pressure alone is sufficient. A rotating movement is often used to obtain �micro cores�. If the needle is kept perpendicular to the probe it is sometimes possible to see micro biopsies enter and move along the needle. Negative pressure is released before removing the needle. If a cytopathologist or cytotechnician is present, the needle should be passed to them (blunt end first or in a tray) to prepare the specimen. Needles washed into fixative should not be used to repeat the aspiration; a new needle should always be used.
Lesions that are radio-opaque can be sampled using screening needle visualisation with fluoroscopic image intensifiers to produce a real-time video images. Fluoroscopy is especially helpful in FNA of peripheral lung lesions. Local anaesthesia of skin and pleura, and needles with a stylet are essential for these deep site aspirates. Modern fluoroscopy equipment with a C-arm is designed to rapidly switch between two planes, enabling needles to be directed to their target quickly and accurately. However, in practice, fluoroscopic guidance is less popular than US or CT guidance as soft tissue lesions are less well resolved.
Modern helical scanners can produce several sections relatively quickly and produce close to real-time images. Single images or small volumes are taken to provide snapshots after each advance of the needle tip for guidance in approaching the target. The tissues of the body are clearly seen with CT scanning, and lesions less than 1cm in diameter located deeply within the body can be reached with precision. The advantage over US guidance is for deeper lesions particularly those obscured on US by intervening gas e.g. lung or abdomen. This is a more time consuming and expensive modality for guidance. The other disadvantages are the temporal delay between needle positioning and imaging and also the limitation to the axial plane for approach.
MRI is rarely used to guide sampling, because patient access is limited by the scanner; special coils giving reasonable operator access, may be used to guided breast aspirates, if the abnormality is only visible using this modality, using non-magnetic needles.
The FNA cytology report is a consultant�s opinion based on the cytological appearances and the pathologist�s assessment of the clinical information provided. The result may not always be definitive, and may raise a suspicion of malignancy rather than a firm diagnosis. It is important that the referring clinician understands the pathologist�s diagnostic confidence or degree of suspicion and what the next step in the diagnostic pathway should be. To this end, it may be useful to use established schemes such as the C1-C5 scheme for breast needle aspirates. Pathologists should always make clear their degree of certainty or otherwise, using a final (bottom line) assessment of �malignant cells present�, �suspicious of malignancy�, �equivocal�, �probably benign�, �benign� or �inadequate� in addition to a free text report. Coding greatly aids correlation with histology and outcome, clinical audit and comprehensive quality management of the FNA service.
A comprehensive FNA service requires sufficient time for audit and quality assurance. Correlation of cytology and subsequent histology should be carried out on an on-going basis or by regular directed audits. The NHS Breast Screening Programme requires detailed monitoring of breast FNA reporting patterns, positive predictive vaules and other quality parameters that can be used to monitor non-screening cases and FNA from other organ sites. At present there is no national EQA programme specific for FNA cytopathology. Specialist reporting is becoming more common in cellular pathology. Pathologists should participate in, and contribute to EQA activities relevant to their specialist areas
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