IMMUNOCYTOCHEMICAL STAINING OF OVARIAN-CYST ASPIRATES WITH MONOCLONAL-ANTIBODY AGAINST INHIBIN

Inhibin is a peptide hormone which is produced by ovarian granulosa ce lls during normal follicular development. It is important that granulo sa cells are recognized in fine needle aspirates (FNAs) of ovarian cys tic lesions, as this allows definite recognition of a functional cyst and exclusion of a potentially neoplastic epithelial lined cyst. Occas ionally the distinction between granulosa and epithelial cells may be difficult, especially when aspirates from functional cysts are unusual ly cellular. In the present study, FNAs from 33 ovarian cystic lesions were immunostained with a monoclonal antibody against inhibin. Nine c ases of peritoneal fluid containing malignant cells in patients subseq uently confirmed to have ovarian adenocarcinoma were also stained. Whe re possible the cytological and immunocytochemical findings were corre lated with subsequent biopsy. In most cases in which cytology suggeste d a functional cyst there was a strong positive staining with anti-inh ibin, although occasional cases were negative. One case originally tho ught to contain epithelial cells stained strongly positive with anti-i nhibin and on review was felt to represent a cellular functional cyst. In all other cases where cells were considered to be epithelial there was no staining with anti-inhibin. The study shows that immunocytoche mical staining with anti-inhibin may be of value in confirming the pre sence of granulosa cells, thus establishing a diagnosis of functional cyst. Although negative staining does not exclude a functional cyst, p ositive staining with anti-inhibin allows exclusion of an epithelial l ined cyst and may avoid unnecessary surgical intervention.