Intramuscular Venous Malformation Associated with Muscle Herniation of the Left Masseter Muscle in a 12-Year-Old Boy.

BACKGROUND Muscle hernias are an uncommon condition typically found in the extremities; masseter muscle hernia is even rarer. However, it is important for clinicians and radiologists to be aware of this possibility. Intramuscular venous malformation (IMVM) is also uncommon and mostly found in the head, neck, and extremities. The simultaneous presence of both conditions is extraordinary uncommon, and, to our knowledge, this has not been reported before in the masseter muscle. Due to their rarity, vague presentation, and inaccurate clinical diagnosis, radiological evaluation is needed to avoid inappropriate surgical planning. CASE REPORT A 12-year-old boy had a long-standing focal left cheek swelling exacerbated by teeth clenching. Lateral X-ray revealed a round calcification over the left mandibular region. Ultrasonography indicated a bulky left masseter muscle with focal heterogeneous structure and 2 rounded calcified foci. During teeth clenching, ultrasonography detected focal muscular herniation through the left masseter muscle facia that reduced with rest. The patient was diagnosed with left masseteric muscle hernia coexistent with IMVM. Surgical excision of the IMVM was performed, and the hernia defect was repaired. Histopathology confirmed the diagnosis, and the patient was discharged without postoperative complications on short-term follow-up. CONCLUSIONS Despite their rarity, masseter hernias and IMVMs should be considered in the differential diagnosis of any masseter lesion, especially in children. We reported a very rare coexistence of both pathologies. Comprehensive diagnosis can be achieved through a combination of clinical examination, X-ray, and ultrasound assessments.