MSH: A tumor of both low- and high-grade malignancy. The low-grade grow slowly, appear in any age group, and are readily cured by excision. The high-grade behave aggressively, widely infiltrate the salivary gland and produce lymph node and distant metastases. Mucoepidermoid carcinomas account for about 21% of the malignant tumors of the parotid gland and 10% of the sublingual gland. They are the most common malignant tumor of the parotid. (From DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p575; Holland et al., Cancer Medicine, 3d ed, p1240),NCI: A carcinoma morphologically characterized the presence of cuboidal mucous cells, goblet-like mucous cells, squamoid cells, cystic changes, and a fibrotic stromal formation. It can occur in several anatomic sites, including parotid gland, oral cavity, paranasal sinus, skin, breast, lung, larynx, and lacrimal ducts. It is classified as low or high grade.