Endocrine Abstracts

Mucoepidermoid carcinomas (MECs) are the most common malignant tumors of the salivary glands. Primary thyroid MECs are extremely rare (about 0.5% of all thyroid malignancies) and, in the majority of cases, are associated with an indolent biologic potential and excellent long-term prognosis. We present the case of a 67-year-old man, with a recently growing anterior cervical mass, associating dyspnoea and fatigue. Thyroid ultrasound revealed an inhomogeneous, hypoechoic mass in the left lobe and multiple pathologic bilateral adenopathies, of up to 3 cm. Cervical and thoracic CT showed a heterogenous mass comprising left thyroid lobe and isthmus, of about 3/6 cm, with a cranial extension which encapsulates the larynx, without an obvious invasion of the laryngeal cartilages; in the lower part, the tumor extends to the left anterior and superior mediastinum and has mass effect on the esophagus. There were multiple nodules in both lungs’ parenchyma compatible with metastasis. The patient was referred to the surgical department and one of the pathological lymph nodes was removed. Histological exam revealed malignant infiltration with ovoid, round and polygonal tumoral cells, eosinophilic cytoplasm, round and ovoid, nucleolated nuclei, pale chromatin, in an island and cribriform pattern. Immunohistochemistry tests showed tumoral cells diffusely positive for CK19, P63, TTF1, PAX8 and negative for thyroglobulin, CD5, Chromogranin A and Synapto, Ki67 positive in 15% of tumoral cells. The diagnosis was metastasis from primary thyroid mucoepidermoid carcinoma. Due to worsening of respiratory symptoms the patient was referred to the pneumology clinic, where he unfortunately passed away just 4 weeks after the initial presentation for endocrinological evaluation.

Conclusions: Although they are usually considered tumors with favorable evolution, sometimes thyroidal MEC may present in an advanced, metastatic stage, associated with a poor prognosis.