Endocrine Abstracts

Introduction: Solid cell nests (SCNs) of the thyroid are considered embryological remnants of the ultimobranchial bodies and the thyroid diverticulum. They are frequently (61–89%) detected in the thyroid gland, but their biological significance remains disputable. According to the fetal cell thyroid carcinogenesis hypothesis SCNs may act as a source for specific thyroid cancer stem cells generating distinct thyroid cancer phenotypes. We report a case of a patient with concurrent SCNs and papillary thyroid carcinoma (PTC).

Case report: A 46-yr-old man presented to the emergency department with a painful mass on the anterior side of his neck. Laboratory tests revealed leukocytosis, while thyroid functions tests, calcitonin, carcinoembryonic antigen and calcium levels were in the normal limits. Neck ultrasound revealed an enlarged thyroid gland with a 2.5 cm dominant nodule on the right thyroid lobe. Fine-needle aspiration cytology showed ‘atypia of undetermined significance’ (AUS). The patient underwent total thyroidectomy. Histological examination revealed a papillary carcinoma 1.4 cm in diameter with central fibrosis, degenerative necrosis and the presence of foam histiocytes. It also showed multiple solid cell nests, nodular hyperplasia and rare lymphoid aggregates in the rest area of the thyroid.

Discussion: Rare cases of concurrent PTC up to 1 cm and SCNs have been described in the literature. SCNs may harbour multipotent stem cells which after a combination of mutations affecting their differentiation and unlimited growth potential may generate cancer stem cells predisposing to thyroid cancer. Immunohistochemical and molecular studies of neoplastic SCN lesions are needed to better understand the complexity of stem cells and their malignant counterparts, advancing our knowledge on thyroid pathophysiology, carcinogenesis, and treatment.