Association of Hyperparathyroidism and Papillary Thyroid Cancer: A Multicenter Retrospective Study

BACKGROUND: Concomitant papillary thyroid cancer (PTC) and hyperparathyroidism (HPT) have been reported in several studies. Our study aimed to investigate the incidence of concomitant PTC in HPT patients upon preoperative diagnosis and present a clinical opinion on detecting thyroid malignancy in case of parathyroidectomy. METHODS: Patients who underwent parathyroidectomy between January 2009 and December 2019 in two medical centers were included. Of the 279 participants 154 were diagnosed as primary hyperparathyroidism (pHPT) and 125 as secondary hyperparathyroidism (sHPT). The incidence of concomitant PTC and its clinical characteristics were compared with 98 patients who underwent thyroidectomy and were diagnosed with classical PTC during the same period. RESULTS: Concurrent PTC was detected in 14 patients (9.1%) with pHPT and in nine patients (7.2%) with sHPT. Ten (71.4%) and seven (77.8%) PTCs were microcarcinomas in the pHPT and sHPT cases respectively. In the pHPT patients, vitamin D was lower in the pHPT+PTC group (13.0±3.7 ng/mL) than in the pHPT-only group (18.5±10.4 ng/mL; P=0.01). Vitamin D levels were also lower in the sHPT+PTC group (12.3±5.6 ng/mL) than in the sHPT-only group (18.0±10.2 ng/mL; P=0.12). In the concomitant PTC group, lymph node ratio was higher than in the classical PTC group (P=0.00). CONCLUSION: A high prevalence of concomitant PTC was seen in patients with pHPT and sHPT. Those concomitant PTCs were mostly microcarcinomas and had more aggressive features, suggesting that efforts should be made to detect concomitant malignancies in the preoperative parathyroidectomy evaluation.