Pulmonary carcinosarcoma masquerading as a cryptic disseminated malignancy.

Pulmonary carcinosarcoma is an aggressive rare malignant tumor comprising a mixture of carcinoma and sarcoma components containing differentiated mesenchymal elements, such as malignant cartilage, bone, and skeletal muscle. We report a case which presented with unusual clinical features and proved cryptic until death. At autopsy, it was a stage IV lung malignancy and histopathology revealed a carcinosarcoma comprising an adenocarcinoma and an osteosarcoma with metastasis to the heart, lymph nodes, and both adrenals. To our knowledge, this is the first case of this subtype with metastasis to the heart. The present case had an unusual clinical presentation and its elusive nature towards diagnosis despite dissemination is noteworthy and unique in the literature.