Solitary Cutaneous Nodule as the Initial Presentation of Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma.

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is an indolent mature B-cell neoplasm that may rarely involve the skin, where it can clinically mimic primary cutaneous B-cell lymphomas (PCBCLs). When the skin is involved, lesions often appear as erythematous or violaceous papules, plaques, or nodules on the head, neck, or trunk. An 85-year-old male presented for evaluation of slowly enlarging, asymptomatic nodules on the right upper back and left posterior shoulder that had been present for many years. A shave biopsy of the right upper back lesion revealed a nodular dermal infiltrate of small lymphocytes. Immunohistochemistry showed CD20, CD79a, CD23, CD5, and BCL2 positivity with low Ki-67, consistent with CLL/SLL. A second-opinion review at the National Institutes of Health confirmed the diagnosis and identified low-level marrow involvement by CLL/SLL. Whole-body positron emission tomography (PET) showed no hypermetabolic lymphadenopathy or visceral disease. The patient underwent excision of the back nodule with complex primary closure, and follow-up examinations have shown a well-healed scar without local recurrence. This case illustrates how CLL/SLL can present with a solitary cutaneous nodule and underscores the importance of histopathology and immunophenotyping in distinguishing secondary cutaneous involvement by systemic lymphoma from PCBCLs, as management and prognosis differ.