Submandibular Gland Epithelial-Myoepithelial Carcinoma with Osseous Metastasis: A First Reported Case and Review of the Literature.

Epithelial-myoepithelial carcinoma (EMC) is a low grade tumor that comprises 1% of all salivary tumors. Local recurrence is not uncommon, but rarely does this tumor demonstrate distant metastasis. We describe a case of a 53-year old female presenting with an asymptomatic, slowly enlarging left submandibular neck mass. Excision of the left submandibular gland (SMG) revealed epithelial-myoepithelial carcinoma with extensive perineural invasion and microscopically positive margins. A subsequent left supraomohyoid neck dissection demonstrated no residual tumor. The patient was stable for one year until a magnetic resonance imaging (MRI) workup for low back pain revealed multiple sclerotic lesions in the iliac crest and lumbar spine, with an iliac crest biopsy demonstrating metastasis. 2.5 year post-operative positron emission tomography-computed tomography (PET-CT) revealed increased [18F]-fluorodeoxyglucose (FDG) avidity in the right iliac crest, pubic symphysis, thoracic and lumbar spine, 9th rib, and sternum concerning for local recurrence and further osseous metastasis. We report the first known case of a submandibular gland EMC with osseous metastasis and highlight the need for prolonged tumor surveillance.