Endocrine Abstracts

JOINT2051

Introduction: Parathyroid tumors are the most frequent cause of primary hyperparathyroidism (PHPT), affecting approximately 0. 1% to 0. 3% of the general population. Most cases are attributed to benign parathyroid adenomas (PA), with hyperplasia being less common, while parathyroid carcinomas (PC) are rare, accounting for less than 1% of cases. Atypical parathyroid tumors (APT) are parathyroid tumors with uncertain malignant potential, distinguished by certain histological features commonly seen in PCs, such as a solid growth pattern, fibrous bands, and cellular atypia. However, they do not exhibit definitive signs of malignancy, such as capsular, vascular, or perineural invasion, or evidence of local invasion or metastasis. Due to the uncertain malignant potential of APT, long-term follow-up is recommended. We followed patients with PA or APT and compared the outcomes in this study.

Methods: This retrospective study includes patients who were followed up in 2 tertiary centres with PA or APT diagnoses between June 2007 and January 2025. Demographic data, including age and gender, along with biochemical parameters serum Ca, corrected calcium (cCa), phosphorus, albumin, alkaline phosphatase (ALP) parathormone (PTH), 24-hour urinary Ca, estimated glomerular filtration rate (eGFR), fractional calcium excretion (FECa), and 25-hydroxyvitamin D (25OHD) were collected. Renal imaging and dual-energy X-ray absorptiometry were used to assess nephrolithiasis and osteoporosis. The patients’ data were compared at the time of diagnosis, preoperatively and at the last follow-up.

Results: 47 patients with APT were compared with 596 patients with PA. Median age was similar (53 years for PA vs. 51 years for APT, P=0. 11). PTH levels were significantly higher in APT (209 ng/l vs. 172 ng/l, P=0. 006), while serum 25-hydroxyvitamin D levels were lower (9. 4 µg/l vs. 14. 9 µg/l, P=0. 03). Other biochemical markers, including FECa, 24-hour urinary calcium, ALP, and corrected calcium, showed no significant differences (P>0. 05). Osteoporosis was more prevalent in APT (64% vs 41. 9%, P = 0. 029), while nephrolithiasis was similar (P = 0. 84). Ultrasonographic tumor volume was significantly larger in APT (1. 65 cm³ vs. 0. 53 cm³, P<0. 001). Follow-up data were available for 309 PA and 35 APT patients. The median follow-up period was 55 months for PA and 75 months for APT (P=0. 88). Serum calcium levels remained similar (9. 12 mg/dL vs. 9. 13 mg/dL, P=0. 368). The incidence of osteoporosis and nephrolithiasis during follow-up was comparable between groups (P=0. 31 and P=0. 76, respectively).

Conclusion: Despite elevated baseline PTH levels, larger tumor size, and suspicious pathological findings, APT demonstrated no significant differences in long-term outcomes compared to PA during follow-up.