[Primary bone leiomyosarcoma. Anatomo-clinical case with immunohistochemistry study and review of the literature].

We describe a primary leiomyosarcoma arising in the proximal part of the right tibia of a 38-year-old man. The diagnosis was confirmed by immunohistochemistry (positivity of tumor cells for alpha smooth muscle actin, HHF 35, desmin and vimentin). To the best of our knowledge, this is the 49th documented case of primary leiomyosarcoma of bone outside the facial skeleton. This exceptional tumor arises more commonly in adults (mean age: 53 years) and in the long bones of lower limbs, near the knee. The most frequent symptom is pain with or without swelling or fracture. Radiological findings invariably consist of a non specific osteolytic lesion. Although their histological appearance does not differ from that of extraosseous leiomyosarcomas, their diagnosis is difficult and often requires immunohistochemical and/or ultrastructural study. From a practical point of view, the diagnosis of primary leiomyosarcoma of bone also requires an intensive review of the case history and of previous pathology. This is necessary in order to eliminate an extraosseous primary site (mainly in uterus, gastrointestinal tract and soft tissues). As well as clinicopathological features, modes of treatment and results are also reviewed.