Page 299 - Textbook of Pathology, 6th Edition

G. LIMITATIONS OF FNAC complement to frozen-section, and is also valuable as an 283
adjunct to histopathology in the typing of lymphomas.
The main limitation of FNAC lies in the fact that only a small
population of cells is sampled by the procedure. The III. CRUSH SMEAR CYTOLOGY
reliability of the test, thus, depends upon the adequacy of
the sample and its representative character. An inadequate Crush smear preparations of tissue particles obtained by
sample which is not representative of the true lesion results craniotomy have been used in the diagnosis of brain tumours. CHAPTER 11
in a ‘false-negative’ diagnosis. If the FNAC report is These smears are preferred by many workers as they allow
‘negative’ despite a strong clinical suspicion of malignancy, recognition of tissue architecture to some degree, in addition
the patient should be investigated further. FNAC may be to better cytological details.
repeated or a surgical biopsy performed to obtain a tissue
diagnosis in such instances. IV. BIOPSY SEDIMENT CYTOLOGY
Lack of requisite clinical information (e.g. size, site and
character of mass) or relevant investigative results (e.g. X- Biopsy sediment cytology entails the examination of
ray findings) further limit the utility of FNAC. Knowledge sediment obtained by centrifugation of fixatives/fluids in
of the exact site from where the aspirate has been obtained which surgical biopsy specimens are despatched to the
is crucial to the accurate interpretation of FNAC smears and laboratory. The method may be useful in the rapid diagnosis
lack of this information severely compromises the ability of of bone tumours as histological sections are usually obtained Basic Diagnostic Cytology
the cytopathologist to provide a diagnosis. after many days on account of the delay necessitated by
decalcification. For soft tissue specimens, the technique offers
no particular advantage.
II. IMPRINT CYTOLOGY
In conclusion, both exfoliative cytology and FNA
In imprint cytology, touch preparations from cut surfaces of cytology have now become a part of diagnostic pathology.
fresh unfixed surgically excised mass lesions are examined. It is imperative for the student in pathology as well as the
Imprints may also be obtained from draining sinuses or clinician to be familiar with the advantages and limitations
ulcerated areas. of cytologic diagnosis. It is acknowledged that a marked
For surgically resected specimens (e.g. lymph nodes) decline in incidence of cervical cancer in developed countries
smears are prepared by bisecting or slicing the specimen and is attributable to highly successful preventive Pap smear
lightly touching or pressing a glass slide onto the freshly screening programme. Similarly, large number of surgical
exposed surface without smearing it. Smears cannot be diagnostic procedures are now avoided by rational use of
prepared from fixed specimens. Smears are wet-fixed or air- FNAC. However, in view of unique responsibility of
dried and stained as per routine. pathologist in patient management, reporting cyto-
The main advantage of the imprint smear is that the cell pathologist should be adequately trained in the skill and
distribution reflects, and to some extent, recapitulates tissue should not hesitate to ask for ancillary diagnostic techniques,
architecture thus aiding in interpretation. The technique is or advise the use of core biopsy or open biopsy, wherever
used in the intraoperative diagnosis of malignancy as a appropriate.

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