mucoepidermoid

Mucoepidermoid carcinoma is a malignant neoplasm that most commonly arises in the salivary glands, though it can occur in other sites with mucous-secreting glands. It is characterized by a mixed cellular composition that includes mucous-producing cells, squamous (epidermoid) cells, and intermediate cells. The relative proportions of these cell types produce a spectrum of histologic grades from low to high grade, which correlates with clinical behavior.

Low-grade tumors are typically cystic with abundant mucous cells and a favorable prognosis, while high-grade tumors are more solid and dominated by epidermoid and intermediate cells with less mucin, showing higher rates of recurrence and metastasis. The grading system guides treatment and prognosis, though tumor stage, perineural invasion, and margin status are also important.

MEC most often involves the parotid gland, but can arise in minor salivary glands, especially of the palate. It accounts for a substantial proportion of malignant salivary gland tumors and has a recognized histopathologic and genetic profile that aids diagnosis.

Genetic features include rearrangements of the CRTC1-MAML2 fusion gene, typically arising from a t(11;19)(q21;p13) translocation. This fusion is frequently associated with better outcomes, particularly in lower-grade tumors, though its prognostic value may vary with grade and stage.

Management typically involves surgical excision with the aim of negative margins, with facial nerve preservation when feasible in parotid tumors. Adjuvant radiotherapy is considered for high-grade tumors, positive margins, perineural invasion, or advanced disease. Chemotherapy is generally reserved for unresectable, recurrent, or metastatic cases. Regular follow-up is required due to risks of recurrence and, in high-grade disease, distant metastasis.