Cells of squamous cell carcinoma in pleural, peritoneal and pericardial fluids. Origin and morphology.

The records of two cytopathology laboratories, covering an aggregate of 33 years, were searched for pleural, peritoneal and pericardial fluids reported as containing cells of squamous cell carcinoma (SCC). This search embraced 9,297 serous fluids from 7,389 patients. Cells of SCCs were found in the fluids from only 46 patients, illustrating the infrequency of such a finding, with most of the SCC cells originating in primary neoplasms of the lung (16), female genital tract (8) or larynx (6). All of the recognized types of SCC cells were found in these fluids. Even so, SCC cells may be mistaken for cells of other neoplasms, such as adenocarcinoma and malignant mesothelioma. SCC cells in serous fluids should be identifiable if careful attention is paid to the morphologic features characteristic of SCC.