We encountered a 38-years-old female patient who was complaining of an unpleasant sensation of the left cervical area due to a recurrent tumor originating from the middle pharynx. She had a history of surgically resected neurofibroma and lipoma from the anterior oropharyngeal wall respectively 5 years and 11 years previously. The preoperative diagnosis of a benign, non-epithelial neoplasm was made based on the imaging studies and surgical treatment was scheduled. An extended surgical resection of the middle pharynx including normal mucosa and a part of the tongue base was successfully accomplished. To cover the pharyngeal defect, a right antero-lateral thigh musculo-cutaneous flap was used for reconstruction. Microscopically, the surgically resected tissue showed a mixed condition of mature cartilaginous, bony and fibroadipose tissue without atypia. The final diagnosis was a benign mesenchymoma which was thought to have developed from pluripotential mesenchymal cells. We considered that the past tumorous lesions had possibly originated in those cells. Because pluripotential mesenchymal cells cannot easily be identified with ordinary histopathological examination, the determination of optimal surgical margins is difficult. In the case of mesenchymoma, substantial marginal tissue should be resected in order to prevent recurrence even in the case of a pathologically-proven benign tumor.