Splenic marginal zone lymphomas of mice

Splenic marginal zone lymphomas (MZLs) have been found to occur at a high f requency in NFS.N mice congenic for high-expressing ecotropic murine leukem ia virus (MuLV) genes from AKR and C58 mice. Based on morphological, immuno logical, and molecular studies of these mice, MZL is clearly recognizable a s a distinct disease with a characteristic clinical behavior. MZL was stage d according to the degree of accumulation and morphological change of cells within the splenic marginal zone, as follows: 1) a moderate Increase in no rmal-looking MZ cells,judged to be prelymphomatous, and 2) MZL in three var iants: i) distinct enlargement of MZ by normal-looking cells (MZL), ii) dis tinct enlargement of MZ by basophilic centroblast-like cells (MZL+), and ii i) extensive splenic involvement by centroblast-like cells (MZL++). The rat e of mitosis and apoptosis increases with lymphoma grade. In most cases, em ergence of a dominant IgH clonal pattern in paired splenic biopsy and necro psy samples was correlated with progression. MZLs were transplantable and h omed to the spleen. MZL may constitute a commonly occurring lymphoma type u nrecognized, in part, because of the centroblastic morphology of high-grade MZL and possible overgrowth of lower-grade MZL by more aggressive follicul ar lymphomas.