Inflammatory pseudotumor of lymph nodes. A distinctive pattern of nodal reaction.

We report seven cases of a previously undescribed, distinctive pattern of nodal reaction resembling inflammatory pseudotumor (IPT) of the lung and other organs. The four men and three women in the series ranged in age from 16 to 62 years (median, 33). All patients presented with prominent lymphadenopathy. Constitutional symptoms were present in five patients, and laboratory abnormalities (especially elevated erythrocyte sedimentation rate, anemia, or hypergammaglobulinemia) in four. All patients recovered (two without treatment) and are alive and well 7-40 months (median, 23) after presentation. Histologically, the process mainly involved the connective tissue framework of the node (hilum, trabeculae, capsule), secondarily spreading into the lymphoid tissue proper and the perinodal soft tissue. It was characterized by a storiform growth pattern, marked vascularity with associated vascular lesions, and a polymorphous reactive cellular infiltrate in a collagen-rich stroma. The differential diagnosis included other reactive processes (Castleman's disease, drug lymphadenopathies), malignant lymphoma (Hodgkin's, peripheral T-cell), histiocytic or reticulum cell lymphomas, and malignant fibrous histiocytoma. Some features of this process appear to be the result of an "acute phase" response; others might be accounted for by a specific target of the initial insult or alterations in the regulation of the inflammatory response to it, rather than by any specific etiologic agent.