Leu-M1 antigen in human neoplasms. An immunohistologic study of 400 cases.

Several studies have shown that the Leu-M1 antigen, a monocyte/granulocyte-related marker, is consistently expressed by the neoplastic cells of patients with Hodgkin's disease (HD). It has been suggested that reactivity of Reed-Sternberg cells with Leu-M1 can be used in support of a morphologic interpretation of HD, and that it is helpful in the differential diagnosis of HD from morphologically similar lesions. To evaluate the significance of the Leu-M1 positivity of Reed-Sternberg cells in the diagnosis of HD, we investigated the distribution of Leu-M1 antigen in a series of patients with HD, non-Hodgkin's lymphomas, and nonhematopoietic neoplasms. We were able to demonstrate the presence of Leu-M1 antigen not only in the majority of patients with HD, but also in 12 of 18 (67%) peripheral T-cell lymphomas, as well as in a variety of nonhematopoietic neoplasms, which included 113 of 199 carcinomas, most of them (58%) adenocarcinomas. Only one of 34 sarcomas showed a focal positive reaction. Leu-M1-related antigen was not detected in any of 18 mesotheliomas, 15 germ cell tumors, 13 melanomas, three schwannomas, or three astrocytomas. Our study indicates that Leu-M1 positivity has no value in supporting the diagnosis of HD in situations where the histologic diagnosis of HD is doubtful. However, since anti-Leu-M1 reacted positively in the majority of adenocarcinomas but was absent in mesotheliomas, melanomas, and most sarcomas, this antigen could serve as a new marker that may be helpful in situations in which carcinoma is a part of the differential diagnosis.