Endocrine Abstracts

Background: Parathyroid carcinoma causes less than 1% of primary hyperparathyroidism and is one of the rarest human malignancies. Clinical symptoms are ambiguous, and the diagnosis is usually made postoperatively based on histopathological examination.

Methods: We present clinical manifestations, pathological features, and follow-up of seven patients from our department after parathyroidectomy performed between 2008 and 2024.

Results: There were two male and five female patients with parathyroid carcinoma whose average age at the time of diagnosis was 54±13.4 years. Osteoporosis was diagnosed in three patients (42.9 %), one of whom had a brown tumour and another had nephrolithiasis. Moreover, one patient (14 %) had osteopenia. Before treatment for primary hyperparathyroidism, the mean calcium concentration was 13.3±1.27 mg/dl, parathyroid hormone 461±283 pg/ml, and phosphorus 2.03±0.57 mg/dl. One patient had a tumour encountered in the left lower parathyroid gland, and six patients had a mass located on the right side of the thyroid gland, five of them near the lower pole and one next to the upper. All patients were diagnosed based on postoperative histopathological examination: the vascular invasions were confirmed in all cases, and the average tumour size was approximately 18 mm (IQR 17–23). None of our patients had regional lymph nodes or distant metastases. Two patients, initially identified as having parathyroid adenomas, were verified to have parathyroid carcinoma after the second surgery (three and seven years after the first operation). Postoperative laboratory examinations revealed a significant decrease in calcium levels (9.57±0.79 mg/dl) and parathyroid hormone concentration (62.1±47 pg/ml), with an increase in phosphorus level (2.97±0.65 mg/dl). The average follow-up time of our patients is 54 months (IQR 30 – 138), and all of them are currently in remission. The patient, who has been followed for the longest time, since 2008, initially required two reoperations due to disease recurrence but has now been in remission for 15 years.

Conclusion: Even though some clinical and biochemical clues may raise the suspicion of parathyroid cancer, the histopathological examination seems to be mandatory to distinguish it from parathyroid adenoma and set the final diagnosis. Because this cancer is so ultra-rare, there is insufficient research in this field, and clinicians must base their treatment decisions mainly on case series. However, the surgery, which may lead to a long-lasting tumour recurrence even when performed at the time of disease recurrence, is undoubtedly the mainstay of treatment.