Pseudolymphoma evolving into diffuse large B-cell lymphoma.

A 46-year-old man presented with a 1-year history of asymptomatic papules on the right arm, without an antecedent event. Initial clinical and histopathologic features were consistent with a pseudolymphoma without gene rearrangements, and the patient was treated with intralesional glucocorticoids. Four months later, the patient developed additional papules and plaques on the right arm, and, at this time, clinical and histopathologic features were most consistent with a T-cell-rich, large B-cell lymphoma, with monoclonal immunoglobulin light chain gene rearrangement. Systemic evaluation showed no evidence of extracutaneous involvement. The transformation of a pseudolymphoma into a large B-cell lymphoma is a rare event. This patient's subtype, diffuse large B-cell lymphoma-other, carries an intermediate prognosis when compared to the more aggressive leg subtype and more indolent folliculocentric subtype. Potential therapeutic options include local radiotherapy, chemotherapy, and rituximab.