Detection of adenocarcinoma in peritoneal washings by staining with monoclonal antibody B72.3

Peritoneal washings are routinely performed in the staging evaluation of carcinomas of the ovary and in "second-look" explorations; major problems in the evaluation of these specimens continue to be the distinction between atypical mesothelium and adenocarcinoma and the identification in an otherwise inflammatory specimen of rare cells of adenocarcinoma, which may be undetected by the most trained individual. Monoclonal antibody (MAb) B72.3, reactive with an oncofetal, tumor-associated glycoprotein (termed TAG-72; MW greater than 1000 kd) expressed in a variety of epithelial malignancies but not generally expressed in benign or malignant mesothelium, was reacted with sections from the paraffin-embedded cell blocks of 185 peritoneal washings from 180 patients with extant cancer or a prior history of malignancy. One hundred four of the washings were initially interpreted as atypical mesothelium, with no evidence of malignancy; when reacted with MAb B72.3, 6 of these specimens demonstrated groups of metastatic adenocarcinoma cells not appreciated by the usual cytologic criteria. Of the 81 washings interpreted as showing cells of adenocarcinoma, 73 demonstrated expression of TAG-72 from both gynecologic and nongynecologic malignancies. In the remaining 49 cases without an associated malignant process, MAb B72.3 did not stain atypical mesothelium, but did react, however, with benign endometrial cells and müllerian inclusions in two cases. MAb B72.3 may be used as a diagnostic adjunct to the routine cytologic evaluation of malignancy in peritoneal washings; reactivity with MAb B72.3 may indicate the need for further evaluation to define the presence of a malignancy or an advanced cancer.