Cytopathology of pericardial effusions.

During a period of four years, 158 cytologic specimens obtained from pericardial effusions of 120 patients were examined. Malignant neoplastic cells were identified in 90 (57%) specimens from 72 (60%) patients. Eighty percent of the neoplasms were epithelial, and 20% were nonepithelial in origin. The most common epithelial tumors were pulmonary (56%) and mammary (39%) neoplasms, and most were adenocarcinomas. In general, the cytologic smears were moderately cellular, with blood and occasional atypical mesothelial cells in the background. There were few reactive cells, such as histiocytes and lymphocytes, in cytologically positive specimens. Pleomorphic nuclei and prominent nucleoli were dominant features of pulmonary adenocarcinomas. Tumor cells of mammary carcinoma were more uniform and often formed cell balls. Epidermoid carcinomas were characteristically poorly differentiated, having a striking resemblance to adenocarcinoma. In most instances, several months elapsed between initial diagnosis of the primary neoplasm and a positive pericardial cytologic finding. The majority of the patients died within ten months after malignant tumor cells were recovered from pericardial effusion. Because of the serious clinical implications, a cytologic diagnosis of cancer in pericardial effusions must never be based on scanty or equivocal evidence. If necessary, any doubt should be resolved by examination of additional material.