Kaposi sarcoma in a non-immunocompromised patient - a potential diagnostic pitfall

Introduction. Kaposi sarcoma is a rare soft tissue tumor that may form masses in the skin, lymph nodes, mucosa and m any other organs. It has a strong male predilection and is usually seen in the older population. It is caused by human herpes virus 8. Risk factors include compromised immune system, typically seen in patients with human immunodeficiency virus infection or organ transplant recipients. Case Report. We report a 66-year-old Caucasian woman with no previous history of hum an immunodeficiency virus infection, immunosuppressive therapy or organ transplantation. She was referred to a plastic surgeon by a dermatologist due to a suspected dermatofibroma presenting with one solitary, firm nodule on the dorsal aspect of the foot that she reported to have occurred a year before. A surgery was scheduled in 6 months, as the tumor was assessed as benign. After excisional biopsy and histological evaluation without immunohistochemical staining, that w as not available, a diagnosis of benign myofibroblastic tumor was made. Later on, a new similar tumor on the hand appeared and the diagnosis was changed into a malignant tumor. Further pathological examination, using immunohistochemical staining, confirmed Kaposi sarcoma. The malignant cells showed positive immunostaining for CD34, CD31, D2-40, WT1, bcl-2, and human herpes virus 8, but they were CD99 negative. Conclusion. Nonspecific clinical presentation and absence of risk factors may mislead the doctors, delay the biopsy and thus delay adequate treatment. In the same time, histological similarities with other disorders and tumors may be challenging for pathologists and lead to wrong diagnosis.