Malignant Mesothelioma in Body Fluids: with Special Reference to Differential Diagnosis from Metastatic Adenocarcinoma

ABSTRACT

BACKGROUND: Malignant mesothelioma (MM) is a rare malignant neoplasm occurring in pleura, pericardium, and peritoneum. The differential diagnosis between MM and metastatic adenocarcinoma (MA) causes diagnostic, staging, and therapeutic dilemmas. Herein, we investigated characteristic cytologic features of MM. METHODS: Cytologic specimens of MM (n=10), MA (n=25), and reactive mesothelial hyperplasia (n=10) were retrieved and reviewed from archival materials in the Department of Pathology, Seoul National University Bundang Hospital from May 2003 to July 2008. RESULTS: MM showed tumor cell clusters and singly scattered malignant tumor cells forming single cell populations with sparse reactive benign mesothelial cells. In contrast, MA showed distinct two cell populations of tumor cell clusters and scattered reactive mesothelial cells. Furthermore, MM frequently exhibited a characteristic long chain-like arrangement (hand-in-hand appearance) and intercellular windows, which were rarely evident in MA. Variable nuclear size, relatively consistent nuclear-cytoplasmic ratio, bior multi-nucleation, and lacy cytoplasmic borders were also frequently observed in MM. CONCLUSIONS: Differential diagnosis of MM from MA in body fluids is possible based on meticulous examination of certain cytologic parameters, which could have significant implications in staging and treatment.