Endocrine Abstracts

JOINT3290

Introduction: Atypical parathyroid tumor (APT) is a rare lesion of uncertain malignant potential with characteristics similar to parathyroid carcinoma, making early diagnosis crucial to adequately plan surgery and follow-up. To date, no predictive criteria exist to differentiate APT from typical adenoma (TA) before surgery.

Aims: To identify predictive preoperative characteristics of TA and APT and compare their biochemical response to parathyroidectomy.

Methods: We retrospectively analyzed patients who underwent parathyroidectomy for primary hyperparathyroidism in our center between March 2022 and August 2024. In patients with TA and TPA, we compared: i) pre-intervention: demographic characteristics, calcium-phosphorus metabolism tests, renal and bone complications, tumor site; ii) post-intervention: type and duration of surgery after excluding patients who also underwent other interventions contextual to parathyroidectomy, histological characteristics, calcium-phosphorus metabolism at discharge.

Results: 150 patients were included (age 59. 5±10. 5 years; 113 females), of whom 14 (9. 3%) had TPA. These patients were predominantly male compared to TA (78. 6% vs. 19. 1%, respectively, P < 0. 001). TPA and TA patients were similar in age and had a higher prevalence of history of other malignancies (50% vs 22. 6%, respectively, P = 0. 02). APT patients had higher calcium levels than TA (11. 7 vs. 11. 2 mg/dL, respectively, P = 0. 03), with no significant differences in other parameters or complications. SestaMIBI scintigraphy localized APT better than TA (100% vs 79. 2%, respectively, P = 0. 04). APT had more frequently a right-sided parathyroid location than TA (92. 9% vs. 50. 7%, P = 0. 003), with no differences in adenoma size. Logistic regression analysis showed that male sex (OR 11. 5, 95%CI 2. 7–47, P < 0. 001) and right-side location (OR 12. 5, 95%CI 1. 4–111, P = 0. 02) or their combination (P < 0. 001) were independently associated with APT. APT patients underwent longer (70±26. 5 vs 52±18. 4 min, P = 0. 007) and more extensive surgery, such as “en bloc” resections and neck exploration (P < 0. 001). APT were heavier as compared with TA (2. 8±2. 9 vs. 1. 2±1. 4 g, respectively, P = 0. 04) and had more fibrosis (P < 0. 001), but no difference in Ki-67 values was found. Finally, APT patients had higher disease persistence and/or recurrence than TA patients (21. 4% vs. 1. 5%, respectively, P < 0. 001).

Conclusion: These preliminary data suggest that TPA and TA have similar preoperative clinical and biochemical presentations. Male gender and/or right parathyroid location appear to be associated with TPA. These patients should be cautioned as they are at higher risk for longer and more complex surgery and postoperative persistence.