Angiomatous Subtype of Penile Kaposi Sarcoma With Concurrent HIV-Negative Multicentric Castleman Disease: A Case Report.

Kaposi sarcoma is a vascular neoplasm driven by human herpesvirus 8 (HHV-8), commonly seen in the setting of immunosuppression, such as HIV/AIDS or posttransplant therapy. The presentation of Kaposi sarcoma in HIV-negative patients with multicentric Castleman disease is exceedingly rare, particularly with uncommon histology subtypes and involvement of the penile shaft. A 58-year-old HIV-negative man with a history of HHV-8-associated multicentric Castleman disease presented with a violaceous lesion on the buttock, followed by a crusted ulcer on the penile shaft. Histopathologic evaluation of the penile biopsy revealed an atypical vascular proliferation lacking spindle cell morphology in classic Kaposi sarcoma. Immunohistochemistry showed positivity for HHV-8, podoplanin (PDPN, clone D2-40), CD34, ERG in the proliferating endothelial cells. The morphologic features and the immunoprofile were consistent with the angiomatous subtype of Kaposi sarcoma. Despite aggressive treatment, the patient progressed to multiorgan failure and died shortly after. This report contributes to the limited body of literature on HHV-8-associated Kapsoi sarcoma in the setting of multicentric Castleman disease in HIV-negative patients. It emphasizes the importance of recognizing angiomatous subtype of Kaposi sarcoma with involvement of unusual anatomical sites.