Large-cell lymphoma. Diagnostic difficulties and case study.

The present report describes the difficulties attending the establishment of a correct diagnosis in an adolescent patient with a large retroperitoneal tumor. It is known that clinical and pathologic findings may sometimes be insufficient to effect a distinction between germ-cell and lymphomatous origin of a large-celled neoplasm. Our purpose is to demonstrate that these difficulties may persist even when current methods of morphologic study, including electron microscopy, are complemented with the application of many antibodies that are commonly available for immunohistologic use. In the young, the differential diagnosis of large-celled neoplasm must include "rhabdoid" tumor, and the poorly characterized nature of this neoplasm compounds the unusually difficult diagnostic dilemma. Our problem case expressed none of many lymphoid tissue markers used, was positive for epithelial membrane antigen (EMA), and was comprised of so-called "anemone" cells visible by electron microscopy, which appearance may correspond to that of carcinomas or lymphomas. Study of gene rearrangement provided additional evidence that the neoplasm was of lymphomatous origin, by showing rearrangement of genes for immunoglobulins. This valuable technique has an important place in diagnostic surgical pathology.