Fibroatosis is a mesenchymal tumor with unclear pathogenesis that are commonly seen in adults. It's characteristics change from benign fibrous lesions to fibrosarcoms with high recurrence and it has ability to increase of size rapidly. Even though its pathogenesis is unknown genetic, endocrine and physical factor are being accused. It can coexist with some other tumors like soft tissue fibroma, polyposis coli, bone tissue tumors, epidermoid tumors, thyroid and gynecological malign lesions. They can be classified as superficial or deep and depending on their anatomical locations. They are found commonly in the shoulder, thoracic wall and mesenterium. The cases originating from aponeurosis of pelvic tissue are seen rarely. In this paper, a case of fibromatosis originating from pelvic tissues was presented. Also the possible reasons for the fibromatosis and its effects are discussed in the light of available literature. © 2009 OMÜ Tüm Haklari Saklidir.