Tehran University of Medical Sciences Journal of Craniomaxillofacial Research 2345-5489 6 4 2020 05 16 165 170 EN Masoud Fallahi Motlagh Azarbayjan Hospital, Urmia, Iran. Yousef Janbaz Oral & Maxillofacial Pathologist. Zahra Mirzaei Department of Oral & Maxillofacial Disease, Medical Sciences of Urmia University, Urmia, Iran. 2020 01 20 2020 04 11 Leiomyosarcoma (LMS) is an uncommon malignant spindle cell tumor of the head and neck region.  It is extremely rare in the oral cavity that arises from smooth muscle differentiation. It may  arise as primary, radiation-associated, or metastatic tumor. The clinical appearance of these tumors  can be deceptively benign and can be mistaken for non-malignant conditions. Here We present a  case with atypical leiomyoma of the mandible in a 40-year- old man who referred with complaint  of pain and swelling in his jaw. He underwent surgery and histology and immonohistochemestery  studies confirmed the diagnosis. After 6 months recurrence occurred. Histologic examination confirmed  leiomyosarcoma so he was managed with surgical excision followed by radiotherapy and  chemotherapy without any recurrence or metastasis after 2 years of follow-up.  Keywords: Leiomyosarcoma; Mandible; Spindle cell tumor. https://jcr.tums.ac.ir/index.php/jcr/article/view/308 https://jcr.tums.ac.ir/index.php/jcr/article/download/308/279