Fine needle aspiration (FNA)
fast and effective
FNA is a procedure performed using a 25 or 23-gauge (0.51–0.64 mm) needle to withdraw a sample
of cells from a mass lesion. The cells are then placed onto glass slides, stained and interpreted by a
cytopathologist.
What lesions are suitable for aspiration?
FNA can be a very useful first-line investigation of both superficial and deep localised lesions for
primary diagnosis, assessment of tumour recurrence and in particular identify those patients that
can be safely followed from the ones that need futher investigation. In the later situation the FNA
results can be helpful in determining the most appropriate further investigation that is required.
Superficial localised lesions that are easily palpable are suitable for FNA. Deep lesions that cannot
be palpated, and lesions within internal organs, can be aspirated using imaging guidance.
Specific lesions for which FNA is contraindicated include suspected carotid body tumour and
phaeochromocytoma due to post-aspiration release of hormones, vascular lesions (haemangioma,
arteriovenous malformations, angiosarcoma) and hydatid cyst.
Interpretation of results
As with any test, correct interpretation of the result requires knowledge of the limitations of the test,
and clinical correlation. In some cases, FNA may be limited by the fact that diagnosis is reliant on
tissue architecture which cannot be assessed, as in histology. FNA may also be limited by the fact
that it is a form of blind sampling and, as some lesions are heterogenous, diagnostic material may
not be aspirated. In these situations clinical correlation is very important. Generally, if there is any
inconsistency between the FNA results and clinical findings, further investigation, such as histology,
should be performed. Ancillary testing of FNA material may be helpful in some cases.
The following are examples where awareness of the limitation of FNA and the importance of clinical
correlation and ancillary tests are emphasised.
Thyroid – A hyperplastic nodule, a follicular adenoma and a minimally invasive follicular carcinoma
have a similar appearance cytologically, reported as suggestive of a follicular neoplasm. Histology is
required for definitive diagnosis as the capsule of the lesion needs to be assessed.
Lymph nodes – Cytologically, low-grade lymphomas can mimic benign reactive lymph nodes.
Hence any lymphadenopathy should be followed clinically and further investigation performed if
the lymphadenopathy does not resolve. Flow cytometry for lymphocyte surface marker analysis
may be helpful.
Metastatic tumours may only partially involve a lymph node which can result in a false negative
diagnosis. Clinical correlation is important and histology may be required.
Breast – It is not possible cytologically to distinguish benign atypia in a papilloma from a papillary
carcinoma, and excision is necessary for these lesions.
Cystic tumours – FNA may sample only the macrophages and fluid of the cystic component
without the diagnostic cells from the cyst lining. Re-aspiration should be performed if a cyst recollects or if any residual mass is present.
Non-diagnostic (unsatisfactory) specimens
A specimen is non-diagnostic if there is insufficient cellular material on the slides for assessment.
This may be due to the nature of the lesion, for example, an extensively necrotic tumour may yield
debris only. Sometimes aspirating the edge of such tumours may help. Some tumours may be
sclerotic and cellular material may not be obtainable.
Non-diagnostic specimens may be the result of the cellular material being obscured by blood
or inflammatory cells. Problems in smear preparation, such as crush artefact or air-drying prior
to fixation can also render specimens unsatisfactory. Close communication with the reporting
pathologist may help to reduce such problems.
These two photographs highlight the necessity for good smear preparation
Well preserved cells in which assessment of nuclear
detail enables a diagnosis of malignancy.
(Pap smear x 40)
Poorly preserved cells as a result of air drying due
to a delay in fixation. Nuclear detail is unable to be
assessed and a diagnosis cannot be made.
(Pap smear x 40)
To obtain an FNA kit
Clinicians may obtain a fine needle aspiration kit, which contains the necessary equipment for
performing an aspirate, by contacting:
Doctor Services or your Medical Liaison Manager
1300 SNPATH (1300 767 284)
Nonpalpable lesions and lesions within internal organs should be aspirated under image
guidance and require referral to a radiologist skilled in the procedure.
Dr Ann Whitehouse FRCPA
Ann graduated from The University of Queensland and trained in histopathology in Victoria, NSW, SA, and
WA. Following several years with Douglass Hanly Moir Pathology, Sydney, Ann returned to Queensland
to work in the private sector, joining Sullivan Nicolaides Pathology in 2001. Ann’s interests include breast
pathology, gynaepathology, and cytopathology.
Dr Whitehouse is available for consultation.
T: (07) 3377 8672
E: ann_whitehouse@snp.com.au
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Meridio 176582 June 2016
Correct at time of printing.
www.snp.com.au
© Sullivan Nicolaides Pty Ltd 2016