A 45-year-old man presents with a 9-month history of a reddish nodule on his foot. Biopsy of the nodule discloses a poorly demarcated lesion composed of fibroblasts and endothelial-like cells lining vascular spaces. Further work-up identifies similar lesions in the lymph nodes and liver. The tumor cells contain sequences of human herpesvirus-8 (HHV-8). This patient most likely has which of the following diseases?

Kaposi sarcoma is the most common neoplasm associated with acquired immunodeficiency syndrome (AIDS). The neoplastic cells contain sequences of a novel virus, HHV-8, which is also known as Kaposi sarcoma-associated herpesvirus. In addition to infecting the spindle cells of Kaposi sarcoma, HHV-8 is lymphotropic and has been implicated in two uncommon B-cell lymphoid malignancies, namely, primary effusion lymphoma and multicentric Castleman disease. Like other DNA viruses, the HHV-8 genome encodes proteins that interfere with the p53 and pRb tumor suppressor pathways. The other choices are hereditary conditions associated with cancer; however, these patients do not typically acquire Kaposi sarcoma. The predominant malignancy seen in patients with ataxia telangiectasia (choice B) is lymphoma/leukemia.Diagnosis: Kaposi sarcoma, AIDS