Intrathoracic rhabdoid carcinoma: a clinicopathological, immunohistochemical, and ultrastructural study of 6 cases.

We evaluated the clinicopathological spectrum of intrathoracic rhabdoid carcinoma, including its immunophenotype and ultrastructural features. Our series included 6 cases arising from the lung (4 cases) and the anterior mediastinum (2 cases). The patients were 4 men and 1 woman aged between 40 and 63 years (median, 53 years). Microscopically, all of the lesions were composed of loosely cohesive, large, atypical polygonal cells, with glassy cytoplasms and eccentric nuclei. Chromatin texture was finely granular or open. On immunohistochemical stain, the neoplastic cells were positive for vimentin in all cases, positive for vimentin, keratins and/or epithelial membrane antigen in all cases, and negative for other antigens. In 1 case, neoplastic cells were also positive for CD34. Electron microscopic study showed prominent perinuclear whorls of densely packed intermediate filaments or mitochondria. All patients were treated with combined chemotherapy and radiotherapy. One patient died 8 months after the diagnosis was made. Of the remaining patients, 3 are alive with evidence of disease progression, including brain metastases. We concluded that rhabdoid neoplasms arising in the thoracic cavity are aggressive tumors of epithelial lineage and should be categorized as true "rhabdoid carcinomas" instead of being ambiguously designated as "intrathoracic rhabdoid tumors" or "carcinomas with rhabdoid phenotype."