Differential expression of CD44s and CD44v3-10 in adenocarcinoma cells and reactive mesothelial cells in effusions

The detection of malignant cells in serous effusions obtained from patients diagnosed with cancer marks the presence of metastatic disease and is associated with a poor outcome. The purpose of this study was to evaluate the role of CD44s and CD44v isoforms in the distinction between mesothelial cells and malignant epithelial cells in effusions. Fifty-nine fresh pleural and peritoneal effusions were studied. These consisted of 41 specimens from patients with known gynecological neoplasms, 9 from patients diagnosed with breast adenocarcinoma, and 9 effusions from patients with various nongynecological malignancies or tumors of unknown origin. Forty-three effusions contained malignant/atypical epithelial cells, and 16 effusions were diagnosed as reactive. Three effusions contained exclusively malignant cells. Specimens were stained with anti-CD44s, v3, v5, v6, v7 and v3-10. The presence of staining in cancer cells, benign mesothelial cells and lymphocytes was evaluated. CD44s immunoreactivity was seen in 10 of 43 (23%) cases in malignant/atypical epithelial cells and in 53 of 56 (94%) cases in benign cells. In contrast, CD44v3-10 was seen in 23 of 43 (55%) cases in malignant/atypical epithelial cells and in 3 of 56 (6%) cases in benign cells. We advocate the use of CD44s and CD44v3-10 immunostaining in diagnostic evaluation of difficult serous effusions.