Diffuse large B-cell lymphoma with primary retroperitoneal presentation: clinico-pathologic study of nine cases.

Diffuse large B-cell lymphoma primarily presenting in the retroperitoneum (PRLBCL) has been the object of occasional reports, all based on dated techniques. MATERIALS AND METHODS: Nine PRLBCLs--with clinical information and paraffin blocks available--were reviewed on morphologic, immunohistochemical and molecular grounds. RESULTS: At microscopic examination, the cases were characterized by a diffuse proliferation of large cells (CD20+, CD79a+, CD3-), displaying a wide rim of cytoplasm (clear in seven instances and acidophilic in two), associated with sclerosis and frequent compartmentalization. Phenotypic and molecular analyses showed that: a) three cases were bcl-2+, bcl-6+, HLA-DR+, and CD10+ (1/3), with associated follicular dendritic cell (FDC) component and bcl-2 gene rearrangements; b) four cases were bcl-2, bcl-6, HLA-DR, CD10, FDC, and bcl-2 gene rearrangement negative; c) two cases had border-line characteristics (bcl-2+, bcl-6+, FDC+, HLA-DR-, CD10-, and bcl-2 gene rearrangement-). The first subgroup was thought to be of follicular derivation, as was the third due to bcl-6 and FDC stains. Of the corresponding five patients, three are in complete remission and two died of disease within 12 months. No obvious, normal counterpart was detected in the remaining four tumors: the corresponding patients died of disease in 3-23 months. The problem of similarities between PRLBCL and primary mediastinal LBCL is discussed. CONCLUSIONS: Although the present series is small, our findings suggest that PRLBCL may represent a more heterogeneous group of tumors than previously thought, which merits further phenotypic and molecular studies to broaden the understanding of its histogenesis and behavior.