MALIGNANT MIXED EPITHELIAL-MESENCHYMAL NEOPLASMS OF THE LUNG

The existence of biphasic neoplasms occurring primarily in the lung is a well-known albeit rare event. The spectrum of malignant tumors disp laying a mixed epithelial/mesenchymal growth pattern is rather narrow when these tumors occur primarily in the lung. The two most often enco untered neoplasms showing features of epithelial and mesenchymal diffe rentiation are carcinosarcomas and pulmonary blastomas. Tumors with an alogous features are of ubiquitous distribution in the human body and have been described in numerous other organs, including the gastrointe stinal tract, the genitourinary tract, and the endocrine system. Altho ugh the histopathologic features of these tumors may seem simple in mo st cases, there appear to be numerous pitfalls in their diagnosis; gra y areas still remain in the characterization of these tumors, because a certain degree of overlap may be encountered with these two conditio ns. Such problems are understandable because the incidence of these tu mors in the general population is very rare. Therefore, one is expecte d to find divergent points of view regarding these neoplasms. It is of importance, however, to unify criteria not only for diagnostic purpos es, but also to determine the prevalence and behavior of these neoplas ms, because such information may provide a rationale for adjustment an d improvement in the treatment and diagnosis of these unusual neoplasm s. We will review past and current concepts regarding these unusual tu mors, as well as their more salient histopathologic features. Copyrigh t (C) 1995 by W.B. Saunders Company