Immunoproliferative small intestinal disease without alpha-chain disease: a pathological study.

Biopsy specimens taken during exploratory laparotomy provided the material for a pathological study of 23 cases of nonsecreting immunoproliferative small intestinal disease (Mediterranean lymphomas without alpha-chain disease). The distinctive pathological feature of immunoproliferative small intestinal disease, i.e., a diffuse lymphoid infiltration, was present in the mucosa and submucosa of all or a major part of the small intestine. It was composed of a low- or intermediate-grade malignant lymphoid proliferation associated in 19 of 23 cases with benign-appearing follicular lymphoid structures. These follicular figures were surrounded and partially destroyed by the lymphoma cells. This association strongly resembles the newly described non-Hodgkin's lymphoma entities of perifollicular or parafollicular cell origin. Gross tumors of the small intestine were found in association with the diffuse lymphoid infiltration in 10 cases. They often constituted foci of lymphoma with a higher grade of malignancy. Mesenteric lymph node involvement was frequent and generally in direct ratio to the severity of intestinal involvement. A comprehensive study of the lesions observed in these cases led to the hypothesis that nonsecreting immunoproliferative small intestinal disease could result from the malignant change of perifollicular B cells; during an initial period the tumoral cells retain circulating and homing properties that explain their infiltrative and extensive method of spreading. The possible subsequent emergence of more aggressive subclones of noncirculating malignant cells could then explain the associated inconstant fungating tumor foci. Further studies using more sophisticated immunohistochemical techniques are necessary to establish the meaning of the hyperplastic lymphoid follicles, the possible etiologic role of benign nodular hyperplasia, the exact identification of the tumor cells, and the relationship of nonsecreting immunoproliferative small intestinal disease to closely related alpha-chain disease.