Parathyroid Carcinoma Causing Mild Hyperparathyroidism in Neurofibromatosis Type 1: A Case Report and Systematic Review

BACKGROUND: Neurofibromatosis type 1 is an autosomal dominant disorder characterized by an increased incidence of tumors, including endocrine ones. Primary hyperparathyroidism can be rarely caused by a parathyroid carcinoma; these patients are generally characterized by severe symptoms, large neck lesions and high levels of PTH and calcium. We report a case of hyperparathyroidism due to parathyroid carcinoma in a patient affected by neurofibromatosis type 1. A systematic review of the literature was also conducted. PATIENT FINDINGS: A 56-year-old woman was referred for a 13 mm-nodular lesion of the neck incidentally discovered on ultrasound examination and mild hyperparathyroidism. A 99mTc-tetrofosmin/pertechnetate subtraction scintigraphy was negative for parathyroid disease. Given the absence of suspicious ultrasound finding, a fine-needle aspiration cytology was performed with iPTH determination in the aspirate, confirming the parathyroid origin of the lesion. The patient underwent left inferior parathyroidectomy with intraoperative monitoring of iPTH and became normocalcemic. On histopathological examination, parathyroid carcinoma presenting at the resection margin was diagnosed, thus a surgery revision was requested. CONCLUSION: Even if literature does not support a syndromic association between neurofibromatosis type 1 and primary hyperparathyroidism, the benefit of precociously diagnosing and treating this condition may outweigh costs associated with screening. This case report moreover demonstrates that sometimes clinical, laboratory and imaging aspects suspicious for cancer may be missing. A prompt referral to a high-volume center is crucial for the management of those cases of incidental histopathological diagnosis.