Lethal midline granuloma (polymorphic reticulosis) and lymphomatoid granulomatosis. Evidence for a monoclonal T-cell lymphoproliferative disorder.

Lymphomatoid granulomatosis (LG) and polymorphic reticulosis (PR), originally described as distinct entities, now are considered as a single disease process. Common histopathologic features include necrosis, vasculitis, and a granulomatous infiltrate. Such features have led to consider lymphomatoid granulomatosis as a systemic vasculitis; alternatively the possible emergence of an overt lymphoma has suggested that it could be a lymphoproliferative process. To investigate this later hypothesis, the authors analyzed the cellular infiltrate of tissue specimens from two patients with histologic features of LG. The analysis included the study of T-cell antigen expression and DNA rearrangement of the beta T-cell receptor gene. In one patient, the T-cell phenotype of infiltrating cells was abnormal because of antigen loss. In both patients, the cells contained rearranged DNA indicating the presence of a clonal T-cell proliferation. It is concluded that some cases of LG and PR, if not all, are related to a neoplastic T-cell lymphoproliferative disorder.