Coexisting Hodgkin's disease and mycosis fungoides. Immunohistochemical proof of its existence.

Hodgkin's disease and mycosis fungoides have been rarely reported in the same patient. This coexistence has been debated in the medical literature. We studied such a patient and report, to our knowledge, the first immunophenotypic evidence for such a coexistence. Reed-Sternberg cells and their variants stained with anti-Leu-M1, Hefi-1, anti-Tac, anti-HLA-DR, and OKT9, but were negative for T cell markers 3A1, Leu-1, Leu-2a, and Leu-3a, a phenotype typical of Hodgkin's disease; infiltrating small lymphocytes were predominantly T cells and were phenotypically normal. In the skin lesions, cells with the phenotype of Hodgkin's disease were not present; the infiltrate was composed of helper T lymphocytes that were 3A1-negative, a phenotype characteristic of the malignant cells of mycosis fungoides. Unexpectedly, a dermatopathic lymph node from the same patient showed the presence of the Leu-M1 antigen on the majority of normal-appearing interdigitating reticulum cells; this was not the case with control dermatopathic lymph nodes from patients without a malignancy. The significance, implications, and possible interrelationships of the findings are discussed.