Endocrine Abstracts

Introduction: Multiple endocrine neoplasia type 1 (MEN1) is a rare hereditary tumour syndrome inherited in an autosomal dominant manner and characterized by a predisposition to a multitude of endocrine neoplasms primarily of parathyroid, enteropancreatic, and anterior pituitary origin, as well as nonendocrine neoplasms. However, thyroid cancer is not part of this syndrome.

Case details: We report the case of a 36-year-old man diagnosed with primary hyperparathyroidism after being referred for mild asymptomatic hypercalcemia. Genetic testing for MEN1, CDKN1B, CDC73 and CASR were requested and an heterozygous variant c.415C>T (p.His139Tyr) classified as pathogenic variant of MEN1 in ClinVar database was detected. The patient underwent subtotal parathyroidectomy and removal of the entire thyrothymic space. The pathology report confirmed three parathyroid glands compatible with hyperplasia and thymic remains. In addition, two of the three incidentally excised nodes were reported as microscopic metastases from medullary thyroid cancer (MTC) based on their morphologic and immunohistochemical profile (positive for CKPan and calcitonin). Serum chromogranin A and calcitonin were normal. After confirming that 24-h urine catecholamines and metanephrines were normal, total thyroidectomy and prophylactic central-compartment neck dissection were performed. The pathology study showed focal parafollicular cell hyperplasia without histological findings of malignancy and ruled out additional nodal metastasis. An additional molecular genetic study of the RET proto-oncogene ruled out germline mutations. Thoracoabdominal CT and hepatic MRI showed new findings of MEN1 related-conditions such as numerous millimetric hypervascular pancreatic nodules in head, body and tail, as well as one adrenal lesion of 16x15 cm with radiological characteristics of adenoma. A 68Ga-DOTATOC PET was ordered and pancreatic foci of pathological overexpression of somatostatin receptors were confirmed, but no other foci suggestive of possible metastasis from MTC. Additional hormonal studies ruled out secretory activity of both pancreatic and adrenal lesions, and a pituitary MRI was normal.

Conclusions: To best of knowledge this is the first case reported in the literature of a patient with MEN1 who has been affected by a concomitant MTC.