Anaplastic diffuse large B-cell lymphoma: a deceptive morphology.

Abstract

An elderly male without significant past medical history presented with cervical lymphadenopathy. Labs showed anemia (Hb 7.6 g/dL) and elevated WBC count (16×10 9 /L) with neutrophilia. Limited core biopsy revealed partial nodal involvement by an overtly malignant proliferation with marked anaplasia including multinucleated forms (A, B) and appeared to display a somewhat cohesive pattern of growth suggestive of an epithelioid neoplasm. Flow cytometry showed no immunophenotypic evidence of lymphoma. The primary differential diagnosis based on these findings included a poorly-differentiated carcinoma versus melanoma, however, immunostains for keratin, Melan A and SOX10 were negative. CD45 was only performed subsequently due to receipt of the case for hematopathologist evaluation given the lymphadenopathy. Surprisingly, the anaplastic tumor cells (A ×40; B ×200; C ×400) were diffusely CD45-positive; subsequent immunostains revealed positivity