Sclerosing mucoepidermoid carcinoma of the parotid gland

Abstract

Mucoepidermoid carcinoma is the most common malignant tumor of the parotid gland. Its clinical behavior is determined by the relative ratio of mucous and epidermoid cells with pathologic high-grade tumors containing a greater proportion of epidermoid cells. Sclerosing mucoepidermoid carcinoma is a rarely reported variant with unclear long-term clinical behavior. A 23-year-old female was found to have a deep lobe parotid mass on imaging studies. Preoperative evaluation was non-diagnostic. Intraoperatively, the tumor was found to be adherent to the lower division of the facial nerve and portions of the posterior digastric muscle. Frozen section specimens showed only squamous metaplasia with background inflammatory fibrosis. Final pathological analysis demonstrated multiple solid and cystic nests and glands within a background of dense, sclerotic, collagenized stroma and inflammatory infiltrate consistent with low-grade sclerosing mucoepidermoid carcinoma. Sclerosing mucoepidermoid carcinoma is a very rare salivary gland tumor with uncertain behavior. Complete surgical excision with tumor-free margins with preservation of the facial nerve (in the absence of clinical invasion) is recommended. Postoperative radiation therapy is suggested for positive or close margins given the adherent nature of the tumor and the risk of recurrence and distant disease found in some case reports. Patients should be followed closely with serial MRI imaging studies of the tumor bed with complete clinical evaluation of the regional lymphatics and chest to evaluate for evidence of recurrence or metastasis.