Primary hyperparathyroidism due to water-clear cell carcinoma of the parathyroid gland: a case report and literature review.

Background: Water-clear cell carcinoma of the parathyroid gland is an exceedingly rare malignancy, with the majority of published cases focusing on adenomas that are typically large and associated with mild elevations in parathyroid hormone (PTH) levels.

Case Description: We present the case of a 43-year-old woman who presented with a pelvic pathological fracture and very high serum calcium of 15.5 mg/dL, along with a severely elevated PTH level (>2,500 pg/mL). Imaging studies, including ultrasound, computed tomography (CT), and technetium-99m sestamibi (99mTc-MIBI) subtraction scintigraphy, revealed a mass in the inferior parathyroid gland on the left side of the thyroid gland. The patient underwent surgical resection, and the excised tumor measured 3 cm × 2.5 cm × 1.5 cm and weighed 10.7 grams. Histopathological examination confirmed the diagnosis of water-clear cell carcinoma of the parathyroid gland, with prominent vascular invasion.

Conclusions: This case is particularly significant as it represents the largest water-clear cell carcinoma of the parathyroid gland reported in the literature to date. The patient was closely monitored postoperatively, and at 1-year follow-up, there were no signs of distant metastases or recurrence of hyperparathyroidism. This case underscores the aggressive nature of water-clear cell carcinoma, highlighting the need for early detection and prompt surgical intervention in such rare and potentially life-threatening tumors.