Atypical parathyroid tumors represent an intermediate entity between parathyroid adenoma and carcinoma and constitute a rare cause of primary hyperparathyroidism. They are characterized by equivocal histological findings, while lacking evidence of malignant involvement. Diagnosis remains challenging and requires both clinical and histopathological correlation. We present the case of a 60-year-old man with a history of gastrointestinal stromal tumor (GIST) treated in 2022 with partial gastrectomy and partial hepatectomy. During routine follow-up, elevated calcium and parathyroid hormone levels were detected. Ultrasound revealed a left inferior parathyroid adenoma measuring 16 mm in diameter. The patient underwent parathyroidectomy. Histological examination demonstrated a tumor with atypical features, consistent with an atypical parathyroid adenoma. There is no evidence of recurrence two and a half years after the adenoma was removed, and the patient remains under surveillance. Atypical parathyroid tumors exhibit features such as nuclear atypia, increased mitotic activity, and fibrous capsule thickness, without the clear vascular or local invasive behavior characteristic of carcinoma. The differential diagnosis between adenoma and carcinoma is difficult but crucial for prognosis and postoperative management. Surgical excision is the treatment of choice, while close postoperative surveillance is necessary due to the risk of recurrence. This case highlights the importance of systematic evaluation of hypercalcemia and the crucial role of histological analysis in diagnosing atypical parathyroid tumors. Despite their relatively favorable prognosis, long-term follow-up is essential for early detection of recurrence.
THEOFILOPOULOU et al. (2026) studied this question.