[Pathological diagnosis of pediatric Burkitt lymphoma involving bone marrow]

To investigate pathologic and differential diagnostic features of pediatric Burkitt lymphoma (BL).

A total of 20 cases of pediatric BL were retrospectively reviewed for their clinical and pathologic profiles. Bone marrow aspiration specimens were available in all cases and bone marrow biopsies were available for immunohistochemical study in 18 cases. Flow cytometry study was available in 16 cases. MYC translocation by FISH method was performed in 11 cases.

Atypical lymphocytes with cytoplasmic vacuoles were found in bone marrow smears in all 20 cases and peripheral blood films in all 19 available cases. The bone marrow biopsies showed infiltration by uniform medium-sized atypical lymphocytes with multiple small nucleoli but without the starry-sky pattern in all 18 cases. Immunohistochemistry showed the following results in all 18 cases: positive for CD20, PAX-5, CD10, CD34 and TdT, but negative for bcl-2 and CD3 with Ki-67 > 95%.Flow cytometry showed CD19+CD20+CD10+FMC7+CD22+TdT-CD3- in 16 cases, including κ+ in 8 cases, λ+ in 7 cases, and κ-λ- in 1 case. MYC gene rearrangement by FISH was observed in 10 of the 11 cases.

The histopathology of BL is distinct, including atypical lymphocytes with cytoplasmic vacuoles in bone marrow aspirate, lack of starry-sky patternin bone marrow biopsy. Generally, the diagnosis should be made with a combined immunophenotype and FISH approach. Pediatric BL must be distinguished from DLBCL and B-cell lymphoma, unclassifiable, which has intermediate features between DLBCL and Burkitt lymphoma.