Do Patients with Atypical Parathyroid Adenoma Need Close Follow-up?

Context: Atypical parathyroid adenomas (APAs) are neoplasms with uncertain malignant potential but lack unequivocal histological signs of malignancy. Objective: This work aims to retrospectively evaluate the clinical and biochemical profiles of patients with APA, the outcome after parathyroidectomy (PTX), and the presence of CDC73 germline and somatic mutations. Methods: This monocentric study was conducted on consecutive patients undergoing PTX for primary hyperparathyroidism (PHPT) between June 2000 and December 2020. Fifty-eight patients with a confirmed histopathological diagnosis of APA, and age- and sex-matched controls with parathyroid adenoma (PA) were also included. Results: Fifty-four patients had sporadic PHPT and 4 had familial isolated hyperparathyroidism (FIHP). Thirty-four patients (59%) had symptomatic disease. Serum calcium and parathyroid hormone (PTH) levels were significantly higher in symptomatic compared to asymptomatic patients (P=.048 and. 008, respectively). FIHP patients were younger than their sporadic counterparts (30±17 years vs 55±13 years). APA patients had significantly higher serum calcium and PTH levels and lower 25-hydroxyvitamin D concentration, bone mineral density, and T score at one-third distal radius compared to those with PA. Four of 56 APA patients displayed a CDC73 germline mutation. No somatic CDC73 mutation was identified in 24 tumor specimens. The mean follow-up after surgery was 60±56.4 months. All but 6 patients (90%), 5 with apparently sporadic PHPT and 1 with FIHP, were cured after surgery. Conclusion: The large majority of patients with APA, despite a moderate/severe phenotype, have a good prognosis. Germline CDC73 mutation-positive patients had a higher rate of persistent/recurrent disease. CDC73 gene alterations do not seem to have a relevant role in the tumorigenesis of sporadic APA.