Histopathological and immunohistochemical study of atypical lymphoid hyperplasia and benign lymphoid hyperplasia of the stomach.

We propose dividing histologically reactive lymphoid hyperplasia (RLH) of the stomach into two categories: atypical lymphoid hyperplasia (ALH), characterized by abnormal follicular architecture and infiltration of atypical lymphoid cells, and benign lymphoid hyperplasia (BLH), where normal follicular patterns are preserved and no atypical cells are found. Using twenty RLH cases (10 ALHs and 10 BLHs), both categories were compared from histopathological and immunohistochemical aspects. Macroscopic division into superficial, thick-walled and nodular types revealed most ALH (80%) to be superficial in character whereas in BLH superficial and thick-walled types were almost equally represented. Lesion size tended to be larger in ALH (greater than 6.1 cm) than in BLH (6.0 cm greater than) cases. As for prognosis after gastrectomy, both categories were favorable. On immunohistochemistry, ALH tended to be strongly labeled by B lymphocyte markers as compared to BLH, where only a weakly positive reaction was expressed. Infiltration of cells labeled by T lymphocyte markers was less conspicuous in ALH than in BLH. From these data, we concluded that ALH and BLH are two distinctive categories of lesion and that ALH has characteristics similar to these demonstrated by malignant lymphoma.