Exploring the molecular insights of concurrent composite mucoepidermoid carcinoma and papillary thyroid carcinoma

Mucoepidermoid carcinoma (MEC) is usually found in salivary glands, where it is the most common primary malignancy. Primary MEC of the thyroid is uncommon, and may occur as a pure lesion or in association with another histological component, most frequently papillary thyroid cancer (PTC). Two types of tumors were described under this category: MEC and sclerosing MEC with eosinophilia (SMECE). MEC shows both squamous and glandular differentiation in the setting of a non-inflamed gland, whereas SMECE is characterized by extensive sclerosis, squamous, and glandular differentiation, a concomitant inflammatory infiltrate rich in eosinophils, and a background of lymphocytic thyroiditis. MECs are more common in young female patients. An understanding of the biology of MEC is limited. Indeed, molecular profiling was performed in only one case of concurrent MEC and PTC. We aimed to determine the molecular profile of concurrent MEC and PTC in a 44-year-old female patient in order to investigate the molecular mechanisms involved in the carcinogenesis of mixed thyroid cancer.