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CD56, the neural cell adhesion molecule (NCAM), is a member of the immunoglobulin superfamily and is associated with cell-to-cell adhesion and migration.1 Among haematological malignancies, CD56 expression has been described mainly in NK/T cell lymphoma, plasma cell myeloma and acute myeloid leukaemia, and rarely in B cell lymphomas, accounting for no more than 0.5% of all B lymphomas.2–8 Malignant lymphoma constitutes <1% of bladder neoplasms and low-grade mucosa-associated lymphoid tissue (MALT) type is most frequent.9 Herein, we describe the first case of primary CD56-positive B cell lymphoma (diffuse large B cell lymphoma, DLBCL) of the urinary system.
The patient, a 60-year-old Japanese woman, presented with recurrent cystitis. Cystoscopy revealed a mass lesion in the urinary bladder. On MRI, this lesion appeared as a sessile tumour protruding into the bladder lumen at the posterior wall, with destruction of the muscularis propria. These images suggested an invasive urothelial carcinoma. Systemic CT, especially of lymph nodes, detected no other suspicious lesions. We performed transurethral biopsy of the bladder tumour after obtaining informed consent.
Histologically, medium to large neoplastic cells with high nuclear/cytoplasmic ratios showed diffuse and/or relatively cohesive proliferations (figure 1A, B). Centrally located, ovoid or irregular-shaped nuclei had a finely dispersed chromatin pattern, occasionally with prominent nucleoli (centroblastic variant). Mitotic figures were numerous (98 per 10 high-power fields). …