Medullary thyroid carcinoma is a special type of thyroid cancer, a pathological type that accounts for a low percentage of thyroid cancers and is moderately malignant. The early symptoms of medullary thyroid carcinoma mainly include palpable lumps in the thyroid gland and metastasis of lymph nodes in the neck, where enlarged lymph nodes can be palpated. Other patients may have specific clinical symptoms due to the secretion of biologically active substances such as calcitonin, prostaglandins and pentraxin, such as a history of chronic diarrhea, or facial flushing, which may be similar to carcinoid syndrome. Some patients with medullary thyroid carcinoma can secrete calcitonin, but their blood calcium does not decrease. Some patients also have paroxysmal hypertension and hypercalcemia due to the presence of pheochromocytoma.