With growing interest in the application of fine-needle aspiration bio
psy (FNAB) in primary diagnosis of benign and malignant lesions, there
has been a significant increase in the use of ancillary studies in th
e aspirated material. To assess the value of such studies, we reviewed
254 morphologically difficult aspiration biopsy cases obtained from d
ifferent sites that underwent ancillary studies which included microbi
ology (MC), special stains (SS), immunocytochemistry (ICC), electron m
icroscopy (EM) and flow cytometry (FC). Correlation with available his
tologic material and/or pertinent clinical information was used as a '
'gold'' standard. In some cases, more than one ancillary study was per
formed on a single aspirate. According to the impact of the ancillary
studies on the final diagnosis, these studies were divided into three
categories: confirmatory/diagnostic (22%), helpful (41%), and non-help
ful (37%). Overall, more studies had positive contributory effect to t
he diagnosis (63%) than those with non-helpful results (37%). Among th
ese adjunct testings, ICC were the most commonly used tests (135/296,
46%), while the EM studies had more positive impact in establishing th
e diagnosis. These findings emphasize the usefulness of ancillary test
ings in FNAB and justify the more selective use of these studies in th
e aspirated material. (C) 1995 Wiley-Liss, Inc.