A unique case of concurrent chronic lymphocytic leukemia/small lymphocytic lymphoma and lymphomatoid papulosis in the same biopsy.

Chronic lymphocytic leukemia (CLL/SLL) is the most common leukemia in the western world and its cutaneous dissemination a very uncommon phenomenon. Lymphomatoid papulosis (LyP) is a CD30+ lymphoproliferative disorder characterized by chronic, recurrent and self healing skin lesions. Up to 20% of patients with LyP have a coexistent lymphoma. While the association between the two entities has been reported, their coexistence has never been documented. We describe a 74-year-old man with known CLL and thrombocytopenia who presented with a 2 year history of recurrent nodules and plaques to both arms and legs that resolved within 4-6 weeks after administration of rituximab and bendamustin for his CLL treatment. His biopsies showed an atypical lymphoid infiltrate, composed of large and pleomorphic cells with a nodular and interstitial pattern in a background of eosinophils. Immunohistochemical staining revealed a pattern of two separate yet coexisting neoplastic processes; a large CD30 positive T-cell lymphoproliferative disorder, while the other one was diagnostic of a neoplastic B-cell process (leukemia cutis). A diagnosis of coexistent LyP and cutaneous involvement by CLL/SLL was rendered. The simultaneous presence of both disorders can be a pitfall in the differential diagnosis of large cell lymphomas, such as Richter's transformation of CLL/SLL.