OBJECTIVETo study the clinicopathologic features, immunohistochemical findings, EBV and c-myc gene status of intra-abdominal non-Hodgkin B-cell lymphoma occurring in children.

METHODSSeventy-four cases of pediatric intra-abdominal non-Hodgkin B-cell lymphoma were retrieved from the archival file. The cases were classified according to the 2008 WHO classification. Tissue microarray including tumor tissues from all the 74 cases was produced. Immunohistochemical study (SP method) for CD20, CD3, CD79a, CD10, bcl-6, MUM1, bcl-2, CD43, CD38 and Ki-67 was performed. In-situ hybridization for Epstein-Barr virus-encoded RNA (EBER) and fluorescence in-situ hybridization for c-myc gene were also carried out.

RESULTSAmongst the 74 cases studied, 65 of them (87.8%) were Burkitt lymphoma (BL), 4 cases (5.4%) were diffuse large B-cell lymphoma (DLBCL) and the remaining 5 cases (6.8%) showed features in-between DLBCL and BL (DLBCL/BL). The patients often presented with abdominal pain, abdominal masses, ileus and intussusception. The ileocecal bowel wall and mesenteric lymph nodes were commonly involved. The lymphoma cells were of high histologic grade and suggested an aggressive clinical behavior. The staining for CD20 and CD79a were positive in all of the cases, while CD3 was negative. The positive rates of CD10, bcl-6, bcl-2, MUM1, CD43, CD38 and EBER in BL were 96.9% (63 cases), 95.4% (62 cases), 0 (0 case), 23.1% (15 cases), 70.8% (46 cases), 96.9% (63 cases) and 41.5% (27 cases), respectively. Fifty-four cases carried translocation of c-myc gene. As for DLBCL, the positive cases of CD10, bcl-6, bcl-2, MUM1, CD43, CD38 and EBER were 3 cases, 2 cases, 3 cases, 2 cases, 2 cases, 2 cases and 0 case, respectively. One of these cases showed c-myc gene translocation. Amongst the 4 cases of DLBCL, 2 of them belonged to germinal center B-cell-like subtype, while the remaining 2 cases were of non-germinal center B-cell-like subtype. The expression rates of CD10, bcl-6, bcl-2, MUM1, CD43, CD38 and EBER in DLBCL/BL were 5/5, 4/5, 0, 3/5, 5/5, 3/5 and 0, respectively. Three of the cases were positive for c-myc gene translocation.

CONCLUSIONSThe majority of pediatric intra-abdominal non-Hodgkin B-cell lymphoma belonged to BL. They have characteristic clinical presentation and sites of predilection and are often associated with an aggressive clinical behavior. Thorough morphologic assessment, immunohistochemistry and in-situ hybridization play an important role in subtyping this group of lymphoid malignancy.