Survivors of childhood cancer risk developing second malignant neoplasms (SMN). a small proportion of SMNs is represented by soft tissue sarcoma (STS), including leiomyosarcoma. The files of the STS Italian Cooperative Group (ICG) were reviewed and 4 patients with secondary leiomyosarcoma were identified, only two of them still alive. In 3 cases, the leiomyosarcoma occurred in the radiation field. The authors found no clear differences between primary and secondary leiomyosarcomas, but leiomyosarcoma proved to be the most frequent SMN registered by the ICG, confirming the need for further studies to identify any distinctive features or syndromes.