Endocrine Abstracts

Background: Routine measurements of serum calcitonin levels are considered an integral part of the diagnostic evaluation of medullary thyroid cancer (MTC). We report a rare case of calcitonin and carcinoembryonic antigen (CEA) negative MTC.

Case presentation: A 63-year-old retired plasterer attending a well mans clinic was referred to the endocrinology service with elevated calcium (2.75 mmol/dl). Systemic examination was unremarkable and there was no endocrine history of note in the family. Repeat calcium at the clinic was 2.76 mmol/l (2.12–2.60) and PTH level was 76 ng/l (10–60). Twenty-four hour urinary calcium was 11.2 mmol/24 h (2.5–7.5).

He was investigated with neck ultrasound and bone densitometry for suspected primary hyperparathyroidism. The bone scan showed osteopenia and the ultrasound showed a 2.5×1.7×1.4 cm dominant left thyroid hypoechoiec nodule with specks of calcification.

Calcitonin level was <11 ng/l. CEA was normal at 4.1 μg/l (<5). Overnight urinary metanephrine and normetanephrine levels were normal 0.06 μmol/mmol creat(0–0.30) and 0.12 μmol/mmol creat (0–0.35) respectively.Plasma metanephrines and normetanephrines were 180 pmol/l (120–1180) and 267 pmol/l (80–510) respectively.

Fine needle aspiration of the thyroid nodule under ultrasound guidance was reported as THY3 and he was referred to the endocrine surgeon.

He underwent bilateral neck exploration along with left hemithyroidectomy. Post surgery his histology report was consistent with MTC and he went onto completion thyroidectomy. RET proto-oncogene mutation is awaited.

Discussion: To this date reports of calcitonin and CEA negative MTCs are rare in the English literature. This case illustrates that the diagnosis of MTC cannot be excluded by means of a negative serum calcitonin. When serum calcitonin is negative a cytomorphologic analysis of fine needle aspiration and RET proto-oncogene mutations are two diagnostic tools which are available for detection and accurate management of patients in whom MTC is suspected.