OBJECTIVETo study the clinicopathologic features and significance of aberrant CD56 expression in diffuse large B-cell lymphoma (DLBCL).

METHODSThe clinical and pathologic profiles of 10 cases of DLBCL with aberrant expression of CD56 were investigated. Immunohistochemical staining, in-situ hybridization for Epstein-Barr virus encoded RNA and gene rearrangement for IgH and Igκ were carried out.

RESULTSThere were 6 male and 4 female patients. The medium age of patients was 46 years. All of them presented with extranodal lymphoma involvement, with gastrointestinal tract being the commonest site (5/10). Histologic examination showed that most of the atypical lymphoid cells were centroblast-like and demonstrated a diffuse growth pattern. Apoptosis and necrosis were identified in some cases. Immunohistochemical study showed that the tumor cells were positive for CD20 or CD79α and aberrantly expressed CD56. Five cases had the GCB phenotype while the remaining cases had the non-GCB phenotype, according to Hans classification. Bcl-6 was positive in most cases (9/10). All cases showed a high proliferation index by Ki-67. The tumor cells were negative for CD3ε, CD138 and granzyme B. In-situ hybridization for Epstein-Barr virus encoded RNA was performed in 7 cases and none of them showed positive signals. IgH gene rearranged bands were detected in 4 cases (4/6) and Igκ was detected in 3 cases (3/6). Follow-up data were available in 8 patients. Two patients died of disease progression within 5 to 13 months after diagnosis and the other 6 patients were alive 8 to 60 months after therapy.

CONCLUSIONSDLBCL with aberrant expression of CD56 is rare. Most of them present with extranodal involvement, show high frequency of bcl-6 expression and high proliferation index. The patients often have good response to chemotherapy.