Laryngeal Neuroendocrine Tumor With Elevated Serum Calcitonin: A Diagnostic and Therapeutic Challenge. Case Report and Review of Literature

Introduction: Laryngeal neuroendocrine neoplasms (NENs) are a rare group of NENs of the neck, which commonly show immunostaining for calcitonin. Laryngeal NENs with calcitonin hypersecretion and lymph node metastases represent a diagnostic and therapeutic challenge, which should be included in the differential diagnosis of medullary thyroid carcinoma (MTC). We report a complex case of laryngeal NEN with calcitonin hypersecretion and a review of the literature.

Case Presentation: A 59-year-old man presented with dysphagia, dyspnea, and lateral cervical mass; he was a smoker. At first imaging, a laryngeal lesion with lateral cervical lymphadenopathies was found, and it resulted as a moderately differentiated neuroendocrine tumor (G2), Ki67 = 5%, positive for calcitonin. Increased levels of serum calcitonin (50 pg/ml) were found. The patient started somatostatin analogs for lesions positivity to somatostatin receptor-based imaging. After 5 months, the disease progressed at 18F-fluorodeoxyglucose ( ¹⁸F-FDG) PET-CT, and also new painful cutaneous lesions occurred. Considering high serum levels of calcitonin, differential diagnosis with MTC was required. Patient performed a thyroid color Doppler ultrasound, nodule fine needle aspiration, calcitonin dosage in fine needle washout fluid, and a calcium gluconate stimulation test. After multidisciplinary evaluation, we decided to perform a total thyroidectomy associated with lateral cervical lymphadenectomy and resection of skin metastases. No MTC was found. Two of the five resected lymph nodes, left upper parathyroid, and skin lesions were metastases of NEN G2, positive for calcitonin. After 2 months, new painful skin lesions occurred, and a target therapy with everolimus 10 mg/day was started. After 6 months of therapy, partial metabolic response with a reduction of 53.7% of radiotracer uptake at primary tumor was detected together with an improvement of patient's quality of life.

Conclusions: The present case is the seventh described in the literature of laryngeal NEN associated with elevated serum calcitonin levels and the first case with parathyroid metastasis, suggesting the importance of a correct differential diagnosis between MTC and calcitonin-secreting laryngeal NEN, using an integrated approach of biochemistry and advanced imaging. This is also the first time that somatostatin analogs and then everolimus were used in this setting, resulting in clinical and partial metabolic response.