Primary cutaneous CD4+ small/medium-sized pleomorphic T-cell lymphoma

Primary cutaneous CD4+ small/medium-sized pleomorphic T-cell lymphoma (also known as primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder) is a rare, indolent form of cutaneous T-cell lymphoma. It is characterized by the proliferation of small to medium-sized CD4-positive T-lymphocytes predominantly involving the skin. The World Health Organization (WHO) has reclassified this entity as a lymphoproliferative disorder rather than a frank lymphoma, reflecting its generally favorable clinical behavior. The condition primarily affects the skin, most commonly presenting as a solitary nodule, plaque, or tumor, typically on the head, neck, or upper trunk. The lesion is usually slow-growing and may be reddish-brown or violaceous in color. Dissemination to extracutaneous sites is exceedingly rare. Histologically, the skin lesion shows a dense dermal infiltrate of small to medium-sized pleomorphic T-cells expressing CD3 and CD4, often with an admixture of reactive B-cells, histiocytes, and other inflammatory cells. The neoplastic cells typically lack CD30 expression. The prognosis for this condition is excellent, with a 5-year survival rate exceeding 95%. Treatment for solitary or localized lesions typically involves surgical excision or local radiation therapy, which are often curative. In cases with multiple lesions, watchful waiting may be appropriate given the indolent nature of the disease. Systemic chemotherapy is generally not required and is reserved for the rare cases with progressive or widespread disease. Regular dermatologic follow-up is recommended to monitor for recurrence.

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