RESUMEN
BACKGROUND: Anaplastic Kaposi's sarcoma (KS) is a rare form of KS characterized clinically by the development of a tumour mass with unusual local aggressiveness and histologically by a specific architecture and cytological morphology. A very small number of limited series in endemic countries have established characteristics common to these anaplastic forms of KS. We present five patients with an anaplastic form in a context of KS ongoing for several years in a non-endemic country. MATERIALS AND METHODS: We collected 5 cases of anaplastic KS followed in our department over a period of 20years. We describe the main developmental, clinical, virological and histological features. RESULTS: The cases involved 4 men and 1 woman whose mean age at diagnosis of anaplastic KD was 70years, with an average time of 25years between initial diagnosis of KD and anaplastic transformation. Our patients were all treated with chemotherapy and/or radiotherapy (RT) prior to diagnosis of anaplastic transformation. All patients had a tumour mass of the lower limbs developing in classically indolent KS with associated chronic lymphoedema. Progression was very aggressive locally with deep invasion of the soft tissues as well as osteoarticular involvement, without visceral dissemination. At present, three patients are dead, one patient is showing partial response, and one patient is in locoregional progression. Diagnosis of the disease was based on histopathological findings. The tumour cells were undifferentiated, pseudo-cohesive, and chiefly organized in sheets. The mitotic count was high (27 mitoses per 10 fields at high magnification). Necrosis was constant. DISCUSSION: To our knowledge, this is the first series describing anaplastic Kaposi's sarcoma in a non-endemic country. The severity of the prognosis, despite the absence of visceral dissemination, is related to the local aggressiveness of anaplastic KS and to its resistance to radiotherapy and chemotherapy, with amputation being required in certain cases.