Masseteric hypertrophy is a relatively uncommon condition which can occur unilaterally or bilaterally, and the etiology is unclear in the majority of patients. Associated with the enlargement of the masseter muscle there is usually bony overgrowth at the angle of the mandible, producing a characteristic quadrangular appearance to the face as in the two patients presented here. Diagnosis is based on awareness of the condition, clinical and x-ray film examinations, and exclusion of more serious conditions. Surgery for correction of the appearance is justified if the patient desires it and should include resection of the enlarged bony portion of the angle of the mandible together with resection of the lower inner portion of the hypertrophic masseter muscle.
Waldhart E, Lynch JB. Benign Hypertrophy of the Masseter Muscles and Mandibular Angles. Arch Surg. 1971;102(2):115-118. doi:10.1001/archsurg.1971.01350020025007