Pseudo-Kaposi sarcoma mimicks Kaposi sarcoma, both clinically and histopathologically. These conditions are due to congenital (Stewart-Bluefarb syndrome) or acquired (Mali) vascular malformations.

The purposes of this study were aimed at evaluating the clinical and histopathological characteristics of pseudo-Kaposi sarcoma and finding differential diagnostic tools from Kaposi sarcoma.

Clinical information of 7 patients with pseudo-Kaposi sarcoma diagnosed in Asan Medical Center from 1989 to 1999 was obtained from the medical records and clinical follow-ups. We re-evaluated 10 biopsy specimens obtained from them and immunohistochemical studies for cutaneous lymphocyte antigen (CLA), CD34, vimentin, and factor VIII were performed with the standard streptavidin-biotin method using paraffin-embedded tissue specimens of 7 pseudo-Kaposi sarcomas and 3 Kaposi sarcomas. In addition, we examined whether human herpesvirus 8 (HHV8) was detected in 3 patients by polymerase chain reaction (PCR).

Six male and one female patients were included. Mean age was 36.3 years. Three patients were classified into Mali type and the other four patients were into Stewart-Bludfarb type. Histopathological examinations revealed capillary proliferation in the upper dermis, perivascular infiltrate of inflammatory cells, extravasated red blood cells, and fibrosis of dermis. Anti-factor VIII and CD34 stained endothelial cells only. CLA was expressed in lymphocytic infiltrate in the epidermis and dermis of pseudo-Kaposi sarcoma, whereas it was negative in Kaposi sarcoma. PCR for HHV 8 showed negative results.

Pseudo-Kaposi sarcoma is an uncommon entity with characteristic clinical and histopathological features. Differential diagnosis between Pseudo-Kaopsi sarcoma and Kaposi sarcoma is important. We suggest that detection of HHV 8 by PCR and imunohistochemical study for CLA may be effective tools in the differential diagnosis between them.