PURPOSE Parathyroid carcinoma (PC) is an exceedingly rare endocrine malignancy with a poor prognosis. Due to the rarity, the natural course and prognostic factors of the disease are yet unclear. Therefore, we aimed to identify the incidence, prognosis, and prognostic factors of PC in the nationwide cohort study.

METHODS The study is a nationwide study using the National Health Insurance Services database in Korea from 2002 to 2017. PC was defined as patients with ICD-10 code of PC and a procedural code for parathyroidectomy.

RESULTS From 2002 to 2017, 255 patients were diagnosed with PC whose mean age was 53.2 years, and 155 (60.2%) were women. The crude and age-standardized incidence were 10.2 and 6.6/10,000,000 person-year in 2016, rising from 4.1 and 3.8/10,000,000 person-year in 2003 (p < 0.001), respectively. The 5- and 10-year survival rates were 86.5 and 72.9%, respectively. In survival analysis, age over 50 years, thyroidectomy at the initial surgery, and reoperation had increased risk of mortality with HRs of 4.83 (95% CI 1.47-15.90), and 4.21 (95% CI 1.60-11.08), and 1.05 (95% CI 1.02-1.08) in multivariate analysis, respectively.

CONCLUSION Incidence of PC has been rising over time, similar to the trends in Western countries. The prognostic factors for mortality were old age, parathyroidectomy alone, and recurrence, emphasizing the importance of preoperative suspicion of the disease. The study is clinically meaningful in the first Asian nationwide study to reveal the natural course of PC.