Unilateral swelling and hyperpigmented papules.

Lymphangioendothelioma, also known as acquired progressive lymphangioma, is a rare vascular neoplasm of lymphatic origin. Although in light-skinned individuals lesions typically present as erythematous to violaceous papules or plaques, in dark-skinned patients lesions often appear hyperpigmented. Histopathologic distinction of lymphangioendothelioma from early Kaposi sarcoma and angiosarcoma is imperative considering the therapeutic and prognostic implications. Herein, we present a 71-year-old woman with slowly progressive hyperpigmented papules and histopathology demonstrating thin-walled vascular spaces interspersed between collagen bundles, consistent with lymphangioendothelioma. We describe the clinical and histologic findings of this rare entity and highlight histologic mimics that might result in diagnostic delay.