Liposarcoma is a particular form of soft tissue sarcoma. First described by Virchow in 1860, liposarcoma is a rare mesenchymal tumor [1]. It represents 14% to 18% of all malignant tumors of the soft tissues and constitutes the most frequent soft tissue sarcoma [2]. For the majority of authors, it affects adult after the fourth decade. Because of the unusual age, we report a case of largeliposarcoma of the dorsal surface of the trunk. The appearance of the operative part made us think of a possible malignancy. A 35-year-old man without a notable patient history was admitted for a mass of the back discovered three years before without any notion of trauma. The patient affirms the recent appearance of an induration motivating the consultation. There were no associated signs such rectorrhagia, hematemesis, emaciation, pain. The physical examination finds a patient in good general condition. Locally, there is a swelling of the right lateral part of the 1/3 middle part of the back. It is an oval swelling of 25 cm long axis. Any fat tumor having a size more than 5 cm must therefore receive special attention even before the fourth decade.