Abstract
Background : Deciduoid mesothelioma is a rare subtype of epithelioid mesothelioma. We report a case of peritoneal deciduoid mesothelioma diagnosed by examination of the ascitic fluid cytology.
Case : A 75-year-old man was detected to have ascites and left axillary lymph node swelling. FDG-PET showed multiple abnormal uptakes in the abdominal cavity. Ascitic fluid aspiration cytology demonstrated large atypical cells and lymphocytes in a clear background. The tumor cells contained centrally located round vesicular nuclei, coarse granular chromatin, prominent nucleoli, and dense cytoplasm. Peritoneal lavage cytology showed small clusters and individual tumor cells intermingled with abundant lymphocytes, and the tumor cells were judged to be mesothelioma cells. Histologically, the omental tumor revealed sheets of large eosinophilic cells with vesicular nuclei and abundant lymphocytes in the stroma. The tumor cells varied in size and nuclear number. The nucleoli were distinct. Immunohistochemically, the tumor cells were diffusely reactive for cytokeratin 5/6, calretinin, D2-40, thrombomodulin and WT1, and partially positive for HBME-1 and mesothelin. The patient received chemotherapy but died of the disease 5 months after the initial presentation. An autopsy was not performed.
Conclusion : Deciduoid mesothelioma cells can be diagnosed by cytology on the basis of the characteristic features of the presence of numerous lymphocytes in the background, abundant cytoplasm, and distinct nucleoli.
