Histological variety of localized lymphoid hyperplasia of the large intestine: histopathological, immunohistochemical and genotypic findings of 16 cases.

Previous reports emphasized that localized lymphoid hyperplasia (LLH) of the large intestine is usually histologically characterized by large lymphoid follicles with striking enlarged germinal centers, and a narrow surrounding mantle zone and marginal zone (MZ). To clarify the histological varieties of LLH of the large intestine, 16 such cases have been studied. The present study demonstrated histological diversity of the LLH of the large intestine including (i) reactive follicular hyperplasia (RFH) (n=8), (ii) RFH with progressive transformation of the germinal center (PTGC) (n=3), (iii) RFH with MZ hyperplasia (n=3) and (iv) RFH with PTGC and MZ hyperplasia (n=2). Overall histomorphological findings of the present series appear quite different from previous descriptions of LLH of the large intestine. The present study showed histological variety of the LLH of the large intestine. Moreover, LLH of the large intestine should be differentiated from extranodal marginal zone B-cell lymphoma and nodular lymphocyte predominant Hodgkin lymphoma as well as follicular lymphoma. Immunohistological studies demonstrated the reactive nature of all 16 lesions. However, three cases showing RFH demonstrated immunoglobulin heavy chain gene rearrangement by polymerase chain reaction study in 12 cases examined. It remains unclear whether these three cases showing RFH could be a sign of the prelymphomatous stage (incipient follicular lymphoma) or representing merely an exaggeration of normal B-cell clonal response in the germinal centers.