Pleomorphic adenoma arising from ectopic salivary glands in the submandibular region: a case report

Pleomorphic adenoma (PA) or mixed tumor, is the most common benign tumor of the major and minor salivary glands. However, PA arising from ectopic salivary gland tissue in the submandibular region is extremely rare with only four case reports described in the English language literature. An 80-year-old Japanese woman presented with a growing mass measuring 25 mm in diameter in the right submandibular region. Magnetic resonance imaging revealed a well-demarcated mass with low intensity on T1-weighted images and high intensity on T2-weighted images with heterogeneous signal intensity. The submandibular gland was compressed, but preserved fat plane was noted at the boundary between the tumor and the gland. The excised specimen was diagnosed as a PA arising from ectopic salivary gland tissue in the submandibular region. This case highlights the diagnostic difficulty of ectopic PA in the submandibular region and the importance of careful preoperative evaluation to avoid unnecessary extensive surgery.