Potential higher malignancy of nonfunctional parathyroid carcinoma: a case series study.

Background: Parathyroid carcinoma is a rare endocrine malignancy. The majority of cases are functional parathyroid carcinoma, while a very small percentage are nonfunctional parathyroid carcinoma. The prognosis for patients with nonfunctional parathyroid carcinoma is generally poorer than that for those with functional parathyroid carcinoma. This is typically due to the insidious nature of nonfunctional parathyroid carcinoma, which often results in late detection and diagnosis.

Case description: Between May 2011 and November 2022, the First Affiliated Hospital of Zhejiang University conducted surgical treatment on six patients diagnosed with parathyroid carcinoma. Of these, two were male and four were female, with ages spanning from 53 to 83 years. The tumors were situated on the right neck in two cases and on the left neck in four cases. The smallest tumor measured 2.5 cm in diameter, whereas the largest measured 11.4 cm. Two cases were exceptionally rare nonfunctional parathyroid carcinomas, and four were functional parathyroid carcinomas. All six patients underwent surgery. Pathological types comprised the chief-cell type in two cases, the mixed-cell type in two cases, the oxyphil-cell type in one case, and the clear-cell type in one case. The follow-up duration ranged from 1 to 151 months. Five patients remained alive, while one patient died. Both patients with nonfunctional parathyroid carcinoma experienced recurrence and metastasis, with Ki-67 levels of 30% and 20%, respectively. In contrast, none of the four patients with functional parathyroid carcinoma recurred, with one case having a Ki-67 level of 20% and three cases with a Ki-67 level of 5%.

Conclusions: The poor prognosis of patients with nonfunctional parathyroid carcinoma may reflect biological behavior and a potentially higher malignant potential. The Ki-67 level is positively correlated with the malignant potential of parathyroid carcinoma. These speculations still need to be validated through large-scale clinical studies.