Endocrine Abstracts

JOINT2557

Background: Calcitonin (CTN)-secreting neuroendocrine neoplasms of the lung are very rare tumors. Differentiating between medullary thyroid cancer and an ectopic source of calcitonin secretion is challenging. Abnormal calcitonin concentrations have been linked to extra-thyroidal sources in neuroendocrine neoplasms located in the pancreas, parathyroid glands, thymus, esophagus, lung, small intestine, adrenal glands, and bladder.

Case: A 54-year-old male patient presented with weight loss, nausea, vomiting, and back pain. He had no other disease and was not on any regular medications. Calcitonin was 1011 ng/l, and CEA was 3.8 ng/ml. Thyroid USG shows an iso-hypoechoic nodule measuring 21x23x24 mm in the right inferior posterior region, containing cystic degeneration areas and macrocalcifications. The nodule’s fine needle aspiration cytology showed atypia of undetermined significance, and the CTN washout was negative. During chest and abdominal imaging, a mass measuring about 45x40 mm was found in the lower lobe of the right lung, and a 56x63 mm mass lesion that showed uneven enhancement was found in the right adrenal gland. Plasma metanephrine levels were normal. We referred him for an 18fluoro-deoxyglucose PET (18FDG-PET), which revealed normal metabolic activity throughout the thyroid. There was high uptake (SUVmax 14.39) within the 4.5 cm mass lesion located in the posterior lower lobe of the right lung and the 6.5 cm mass lesion in the right adrenal gland (SUVmax 10.77). A biopsy diagnosed the patient’s lung mass as pulmonary neuroendocrine carcinoma. Malignant cells were positive for CD56, synaptophysin and calcitonin. Staining for chromogranin A and Napsin A was negative. The Ki-67 proliferation index was high at 70%. The medical oncology department initiated systemic chemotherapy. Follow-up imaging after chemotherapy showed progressive disease.

Conclusion: This case highlighted the complexity of the differential diagnosis of hypercalcitoninemia, more particularly the difficulty of distinguishing between medullary cancer and a tumor with ectopic calcitonin release. The different diagnoses are important since treatment and prognosis are different. The approach to hypercalcitoninemia requires a multidisciplinary one. It is important to perform a complete clinical evaluation of these patients so that ectopic calcitonin-secreting tumors are not overlooked.