Objective: Primary cutaneous T-cell lymphoma with aberrant expression of cluster of differentiation (CD) 20 is an exceedingly rare manifestation of cutaneous T-cell lymphoma that is easily misdiagnosed as B-cell lymphoma. The significance and prognostic implications of T-cell neoplasms demonstrating the classic CD20 B-cell marker have yet to be elucidated.

Methods: We present a case of primary cutaneous T-cell lymphoma with aberrant CD20 expression in a 97-year-old male who presented with a 2-year history of pruritic plaques and nodules covering his body. Nodule biopsy demonstrated a dense, atypical dermal T-lymphocytic infiltrate consisting of predominantly large cells exhibiting classic T-cell markers (CD4 and CD3) along with aberrant expression of the B-cell marker CD20 (expressed in late pro-B to mature B cells).

Conclusions: The patient was tentatively diagnosed with primary cutaneous CD30-negative large T-cell lymphoma with aberrant CD20 co-expression, pending workup to exclude systemic lymphoma with cutaneous involvement. He unfortunately passed away 4 days after the initial dermatologic presentation. Conclusions: The prognostic implications of CD20-positive T-cell lymphoma require further exploration, along with the potential role of CD20 antibody in treatment of this rare malignancy.