Primary extranodal diffuse large B-cell lymphomas: Many sites, many entities? Clinico-pathological, immunohistochemical and cytogenetic study of 106 cases

We analyzed the clinicopathological, immunohistochemical and cytogenetic features of 106 extranodal (EN) diffuse large B-cell lymphomas (DLBCLs) from stomach (34 cases), intestine (10), cervico-cephalic region (11), central nervous system (13), testes (21), skin (8), and miscellaneous sites (9). Hans’ algorithm and the immunohistochemical double expressor score (DES) for MYC and BCL2 were applied to all cases. A subset of fifty-eight cases were analyzed with fluorescent in situ hybridization (FISH) with specific break apart probes for BCL6, MYC, BCL2, CCND1, BCL10 and MALT1 genes. Clinical records were available for all patients. The immunohistochemical study showed that, in our series of EN-DLBCLs, the Hans’ subgroup and the DES differed significantly according to the site of origin. At FISH analysis, BCL6 and BCL2 were the most commonly rearranged genes in non-GC and in GC cases, respectively. Gastrointestinal lymphomas displayed the highest rate of gene rearrangements, often with MYC involvement. One testicular DLBCL showed BCL2/MYC double hit. At survival analysis, cerebral and testicular origin was associated with poor prognosis. In addition, Hans’ subgroup and other immunohistochemical markers influenced patients’ outcome. In conclusion, our data suggest that immunophenotypic, genetic and survival characteristics of EN-DLBCL are related to the specific primary site of the disease.