Intramyofiber invasion in a case of oral squamous cell carcinoma; an unusual pattern of skeletal muscle infiltration

Tumor infiltration in the skeletal muscle is a rare entity and usually associated with aggressive tumor phenotype. Intramyofiber skeletal muscle invasion is the rarest pattern of muscle invasion, where the architecture of the individual myofibers remain preserved. This uncommon pattern of skeletal muscle invasion has occasionally been identified in Ewing sarcoma, non-Hodgkin lymphomas and leukemias however there are sparse literatures available on carcinomas showing intramyofiber pattern of invasion. They can closely mimic myositis and can be missed on low magnification. Thus, careful examination in high magnification supported by immunohistochemistry can resolve the issue. Here we present one case of intramyofiber skeletal muscle invasion in oral squamous cell carcinoma.