Asymptomatic giant intrathyroid parathyroid carcinoma and common parathyroid carcinoma: two case reports and literature review.

BACKGROUND: Parathyroid carcinoma (PC) is a rare, slow-growing but locally aggressive endocrine malignant tumor. Its clinical diagnosis is difficult, especially intrathyroid parathyroid carcinoma with atypical or asymptomatic symptoms. It is difficult to make a clear diagnosis before and during surgery. CASE DESCRIPTION: A 27-year-old female with elevated parathyroid hormone for 1 month showed a hypoechoic nodule immediately behind the middle of the left lobe of the thyroid gland. Laboratory work showed mild elevations in blood calcium and parathyroid hormone. She underwent parathyroid adenoma resection and thyroidectomy and functional central lymph node dissection. Her symptoms resolved after the operation and her recurrence rate remained negative at 20 months of follow-up. Another 74-year-old female patient with giant intrathyroid parathyroid carcinoma developed recurrence and metastasis only 5 months after undergoing radical thyroid cancer and total thyroidectomy. CONCLUSION: We compared the differences in clinical manifestations, imaging, pathological features, treatment and prognosis between two cases of parathyroid carcinoma without obvious clinical symptoms.