Identification of adenocarcinoma in cytospin preparations of effusions using monoclonal antibody B72.3

Metastatic adenocarcinoma in human effusions can be difficult to distinguish from reactive mesothelial cells, particularly if the malignant cells are rare, have bland cytologic features, or occur as single cells rather than clusters of cells. Monoclonal antibody (MAb) B72.3, generated against a membrane-enriched fraction of breast carcinoma, has been shown to be reactive with formalin-fixed, paraffin-embedded tissue sections of human breast and colon carcinomas but not with sarcomas, melanomas, hematopoietic neoplasms, or a variety of normal adult tissues. The authors have adapted the avidin-biotin-immunoperoxidase method using MAb B72.3 to evaluate cytospin preparations of pleural and peritoneal effusions for the presence of adenocarcinoma cells. The cytospin method was selected because it provides a rapid, efficient, and inexpensive means of evaluating effusions for cellular content. Reactive effusions from patients with no history of adenocarcinoma as well as obviously malignant effusions from patients with documented adenocarcinoma were studied. MAb B72.3 demonstrated no reactivity with any of the variety of cell types in the reactive specimens from patients without a history of adenocarcinoma. In contrast, in all of the malignant effusions studied, 10-90% of the nonhematopoietic cells demonstrated reactivity with MAb B72.3. In addition, MAb B72.3 highlighted occult adenocarcinoma cells in cytospin preparations of effusion fluids from patients with a primary diagnosis of adenocarcinoma in which no definite malignant cells could be identified using standard cytologic criteria.