Pulmonary carcinosarcoma characterized by small round cells with neuroendocrine, myogenic, and chondrogenic differentiation: An extremely rare case.

ABSTRACT

Carcinosarcoma is a clonal tumor developed through sarcomatoid changes in a carcinoma via the epithelial-mesenchymal transition (EMT). Here, we present an extremely rare case of pulmonary carcinosarcoma characterized by components suggesting pluripotency, namely neuroendocrine, myogenic, and chondrogenic differentiation, based on immunohistochemical analysis. A 42-year-old Japanese man was admitted to our hospital. Analysis of tumor tissue after right upper lobe lobectomy revealed a transition between carcinomatous and sarcomatous components. Immunohistochemical analysis suggested immortality owing to complete loss of p53 and diffuse expression of p16 in both the carcinomatous and sarcomatous components. There were also scattered cell groups expressing aldehyde dehydrogenase 1 family member A1, SOX2, CD133, and c-kit, suggesting the possible presence of cancer stem cells. Our findings in this case suggested that the EMT may play a key role in mediating the immortality of tumor cells in carcinosarcoma and facilitating the pluripotency of cancer stem cells.