Extramedullary CD20-positive B-lymphoblastic lymphoma in a 5-year-old child: A diagnostic challenge.

Lymphoblastic leukaemia/lymphoma may present as an isolated extramedullary mass, which includes the musculoskeletal region involvement with normal or near-normal blood counts. The tumour may be in the form of B or T-lymphoblastic leukaemia/lymphoma. The clinical features and histological morphology of extramedullary B-lymphoblastic lymphoma (B-LBL) may mimic mature B-cell neoplasms, thus posing a diagnostic challenge. Arriving at the right diagnosis is crucial because these two diseases differ in their prognosis and management. A high index of suspicion is therefore important so as not to miss the correct diagnosis. The diagnosis may be overlooked because the clinical presentation may not be typical of B-LBL or the blood counts do not show any abnormalities. In this report, we highlight one such case where the diagnosis of B-LBL was missed because of its atypical presentation.