Immunohistochemical and ultrastructural study of a pulmonary carcinosarcoma (biphasic sarcomatoid carcinoma) with rhabdomyoblastic differentiation

Histologic, immunohistochemical and ultrastructural features of a case of carcinosarcoma of the lung are described. The biphasic pattern of this neoplasm is characterized by the presence of a carcinomatous component that corresponds to an adenosquamous carcinoma, and a sarcomatous component with rhabdomyoblastic differentiation. Since the biphasic sarcomatoid carcinoma has an aggressive clinical behaviour, immunohistochemical expression of prognostic markers, such as Ki-67 and p53 is evaluated to individuate differences between the carcinomatous and the sarcomatous components of the tumor. The higher p53 expression and Ki-67 positivity in the former, suggests that the carcinomatous component probably represents the more aggressive portion of the tumor. Moreover, P53 expression is nuclear in both carcinomatous and sarcomatous areas, thus it is likely that the biphasic sarcomatoid carcinoma of the lung is monoclonal in origin.