A Case of Long-undiagnosed Classic Kaposi's Sarcoma with Extensive Skin Eruptions

Kaposi's sarcoma (KS) is a chronic, multifocal lymphoangioproliferative tumor that occurs mainly in older individuals in the Mediterranean region. KS is often observed as a malignant tumor in patients with acquired immunodeficiency syndrome, and classic KS is rare. An 82-year-old man was referred to our department with bilateral lower-leg edema with purpura and small nodules. When the patient was in his mid-50s, edema with purpura appeared in his lower extremities without any specific trigger. Eight years earlier (in his mid-70s), the purpura lesions gradually turned nodular. A similar skin rash appeared on the forearms and back of the hands two years earlier. Physical examination revealed diffuse brown pitting edema over the entirety of the lower extremities and extending from the dorsum of the bilateral hands to the elbows. Multiple purple-red, elastic, hard nodules ranging from a few millimeters to about 1 cm were localized and fused over the edema. Histological examination of the forearm nodule revealed proliferation of collagen fibers and cellular infiltration in the dermis. The intricately proliferating cells in the dermis were spindle-shaped with round nuclei. Immunohistochemical staining revealed spindle-shaped cells positive for CD31, CD34, and D2-40. These cells were positive for human herpesvirus (HHV)-8 and negative for human immunodeficiency virus (HIV) antigens and antibodies. He was diagnosed with classic KS. We proposed chemotherapy, but he refused to receive any treatment. Our patient did not receive any immunosuppressive therapy, and the HIV test result was negative. Therefore, immunosuppressive status may not be involved in the development of KS in our patient. He had opportunities to consult dermatologists but was never diagnosed with KS. A skin biopsy helps diagnose KS; thus it should be considered when a patient experiences long-standing, slowly progressive, unexplained leg edema accompanied by a skin rash.