A 40-year-old man comes to the office due to lesions over his thigh that he first noticed 2 weeks ago. The lesions are neither painful nor itchy. The patient has a history of HIV infection. He has not been compliant with HIV therapy. On physical examination, the patient appears mildly cachectic. Vital signs are normal. There are 2 elliptical, raised, nontender, violaceous lesions on his right thigh. No other skin or mucous membrane lesions are present. There is no lymphadenopathy. CD4 count is 100/mm³. The patient's skin condition most likely originated from which of the following cells?

Question

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This patient with a history of HIV infection and a current CD4 count of 100/mm³ now has 2 lesions on the right thigh that are violaceous, raised, and nontender. This presentation is classic for Kaposi sarcoma (KS), the most common tumor in HIV-positive individuals, which usually presents as multiple red, purple, or brown papules or plaques and appears first on the lower extremities before spreading proximally. KS is a vascular tumor that is strongly associated with both HIV and human herpesvirus type 8 (HHV-8). HHV-8 infects vascular and lymphatic endothelial cells, causing them to differentiate into a mixed phenotype thought to increase oncogenic potential. The HHV-8 genome contains several viral oncogenes that inhibit cell cycle regulation and apoptosis, thereby promoting endothelial cell growth and tumorigenesis. Biopsy of cutaneous KS typically reveals a dermal proliferation of spindle-shaped endothelial cells with slit-like vascular spaces, red blood cell extravasation, and inflammation. (Choice A) Basal cell carcinomas arise from basal keratinocytes, typically due to ultraviolet radiation-induced mutations. Lesions are commonly pink or skin-colored (vs violaceous), pearly or translucent, and located in sun-exposed areas such as the face (vs the thigh). (Choice C) Cutaneous mastocytosis is caused by the pathologic accumulation of mast cells within the skin, which, in adults, is often associated with systemic mast cell proliferation (ie, systemic mastocytosis). Skin involvement typically manifests as monomorphic, reddish-brown macules that gradually proliferate and spread over months to years; because of histamine release, the lesions characteristically develop erythema or urticaria when scratched. (Choice D) Sweet syndrome (ie, acute febrile neutrophilic dermatosis) is a rare inflammatory disorder associated with pathologic neutrophilic infiltration into the skin. Because of their inflammatory nature, lesions are typically erythematous, edematous, and tender; ulceration like that of pyoderma gangrenosum (another neutrophilic disease of the skin) may occur. Lesions are classically accompanied by frequent fever. (Choice E) Melanocytic nevi are caused by the benign proliferation of nevus cells, a type of melanocyte that forms clusters instead of single units evenly dispersed throughout the skin. Acquired melanocytic nevi may be elliptical, raised, and nontender; however, they are not typically violaceous, and most appear in childhood or adolescence (vs adulthood). Educational objective: Kaposi sarcoma often presents as multiple red, purple, or brown lesions on the lower extremities in patients with HIV infection. It is a vascular tumor caused by human herpesvirus type 8 infection of endothelial cells. __________ References: HIV-associated Kaposi sarcoma and related diseases. (http://www.ncbi.nlm.nih.gov/pubmed/28609402)

A 40-Year-Old Man Comes to the Office Due to Lesions