Masticator Muscle Tumor Infiltration

Epidemiology

Malignancies originating in spaces and structures adjacent to the masticator space can involve the masticator muscles. Nasopharyngeal carcinoma frequently spreads into the masticator space to involve principally the medial pterygoid muscle. Tonsillar carcinoma or neoplasms arising from the mandible can also infiltrate the medial pterygoid muscle.

Clinical Findings

At presentation, the symptoms and signs of masticator muscle infiltration are frequently overshadowed by the primary tumor. However, on questioning, a history of trismus can be elicited. Clinical examination may also show varying degrees of limited mandibular excursion.

Pathology

In most cases, malignant infiltration is confined to the muscle adjacent to the primary tumor. However, neoplastic infiltrates may spread farther afield to involve the muscle in a permeative way. In some patients, involvement of muscle bundles leads to tumor spread along the mandibular nerve resulting in proximal extension through the foramen ovale. Squamous cell carcinomas and adenocystic carcinomas have a propensity to spread in this manner.