Primary Cutaneous Diffuse Large B-cell Lymphoma, Leg Type, With Rapid Systemic Progression in an Elderly Patient: A Case Report

Primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL-LT), is an aggressive neoplasm characterized by a high proliferative rate and a tendency for systemic dissemination. It typically presents in older adults as erythematous nodules or plaques on the lower extremities. We report the case of a 77-year-old man with a nodular lesion on the right leg of seven months' duration, which progressed to multiple confluent nodules forming a plaque with necrotic areas. Histopathological examination revealed a diffuse infiltrate of large cells expressing CD20, BCL-2, and MUM-1, with a high Ki-67 proliferation index. Based on the clinical, histopathological, immunohistochemical, and staging findings, a diagnosis of PCDLBCL-LT, stage T2aN0M0, was established. Following six cycles of R-CHOP immunochemotherapy and consolidative radiotherapy, the patient developed disease progression with bone marrow involvement and progression to systemic disease. This case highlights the aggressive clinical behavior of this entity and the need for close follow-up.