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 techn iques. Materials and methods: Nine PRLBCLs - with clinical information and paraffi n blocks available - were reviewed on morphologic, immunohistochemical and molecular grounds. Results: At microscopic examination, the cases were characterized by a diff use proliferation of large cells (CD20(+), CD79a(+), CD3(-)), displaying a wide rim of cytoplasm (clear in seven instances and acidophilic in two), as sociated with sclerosis and frequent compartmentalization. Phenotypic and m olecular analyses showed that: a) three cases were bcl-2(+), bcl-6(+), HLA- DR+, and CD10(+) (1/3), with associated follicular dendritic cell (FDC) com ponent 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 bord er-line characteristics (bcl-2(+), bcl-6(+), FDC+, HLA-DR-, CD10(-), and bc l-2 gene rearrangement(-)). The first subgroup was thought to be of follicu lar derivation, as was the third due to bcl-6 and FDC stains. Of the corres ponding five patients, three are in complete remission and two died of dise ase within 12 months. No obvious, normal counterpart was detected in the re maining four tumors: the corresponding patients died of disease in 3-23 mon ths. The problem of similarities between PRLBCL and primary mediastinal LBC L is discussed. Conclusions: Although the present series is small, our findings suggest tha t 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.