Recurrent "syncytial variant" of Hodgkin's disease: an immunohistologic diagnosis.

A case of recurrent Hodgkin's disease of the "sarcomatoid" or "syncytial variant" type was seen that occurred as an extension from the mediastinum to a previously uninvolved extranodal site (breast) and pericardium after treatment of classical nodular sclerosing Hodgkin's disease based in the lymph nodes. This histologic variant was composed of sheets of large, undifferentiated neoplastic cells with few, if any, diagnostic features of nodular sclerosing Hodgkin's disease. For this reason, the differential diagnosis of this variant was difficult and included non-Hodgkin's lymphoma (peripheral T-cell lymphoma), Ki-1-positive lymphoma, medullary carcinoma, metastatic carcinoma, melanoma, and granulocytic sarcoma. Immunologic analysis by immunoperoxidase technique showed a phenotype consistent with "syncytial variant" Hodgkin's disease: Leu-M1+, Ki-1+, IL-2+, HLA-DR+, T11-, pan B-, K-, lambda-, cytokeratin-, S-100-, muramidase-.