The ultrastructural diagnosis of diffuse large-cell ("histiocytic") lymphoma. Fine structural study of 30 cases

Thirty cases of diffuse large-cell ("histiocytic") lymphoma were studied with the electron microscope. The purpose was to define the criteria requisite for the ultrastructural diagnosis of large-cell lymphoma. The fine structural features of the lymphoma cells were compared to those of similar appearing reticuloendothelial neoplasms and other tumors that may simulate large-cell lymphoma by light microscopy. Two variants of large-cell lymphoma were recognized, each composed of neoplastic lymphoid cells with the morphologic features of transformed lymphocytes. The larger group represents large noncleaved cell lymphoma of Lukes and Collins' functional classification, while the second type corresponds to lymphoma of large cleaved cells. The ultrastructural features of large-cell lymphoma are uniform and usually easily identified. By utilizing diagnostic electron microscopy, large-cell lymphoma can often be distinguished from similar appearing tumors presenting as diagnostic problems at the light microscopic level.