mucoepidermoide

Mucoepidermoid carcinoma is the most common malignant tumor of the salivary glands. It arises from pluripotent ductal epithelium that differentiates into mucin-producing (mucous) cells, squamous (epidermoid) cells, and intermediate cells. The tumor can involve major glands, most often the parotid, as well as minor salivary glands throughout the oral cavity and oropharynx.

Clinically, it presents as a painless swelling; rapid growth or facial nerve involvement may occur with parotid tumors. Symptoms and course vary by histologic grade, with low-grade tumors typically behaving less aggressively than high-grade ones.

Histologically, mucoepidermoid carcinomas are composed of a variable mix of mucous, epidermoid, and intermediate cells. They are graded as low, intermediate, or high based on cystic versus solid growth, proportion of mucous cells, cellular atypia, mitotic activity, necrosis, and perineural invasion. Low-grade tumors tend to be cystic with abundant mucous cells; high-grade tumors are more solid and show prominent atypia.

Genetic features include a characteristic translocation t(11;19)(q21;p13) resulting in MECT1-CRTC1 (also called CRTC1-MAML2) fusion, or related MAML2 fusions. This genetic alteration is associated with a better prognosis and can aid diagnosis.

Diagnosis involves imaging to assess extent, followed by histopathology; fine-needle aspiration can suggest mucoepidermoid carcinoma but may be inconclusive.

Treatment is primarily surgical: complete excision with negative margins. In the parotid gland, this may require superficial or total parotidectomy with facial nerve preservation when feasible; neck dissection is considered for clinically involved nodes. Adjuvant radiotherapy is used for high-grade tumors, positive margins, perineural invasion, or advanced stage. Chemotherapy has no established role in routine management.

Prognosis depends on grade and stage; long-term follow-up is essential due to risk of recurrence and potential late metastasis.