Stage 1 medullary carcinoma of the thyroid is more serious. Medullary carcinoma is of moderate malignancy and has a poor prognosis, but stage 1 is early, and aggressive treatment can improve the prognosis or even eradicate it. Thyroid cancer can be divided into papillary carcinoma, follicular adenocarcinoma, medullary carcinoma and undifferentiated carcinoma according to pathological findings. Papillary carcinoma is the most important type with low malignancy; follicular carcinoma has medium malignancy and worse prognosis than papillary carcinoma, and both of them are collectively called differentiated thyroid cancer. Medullary carcinoma is moderately malignant and prone to cervical lymph node invasion and hematogenous metastasis. Its prognosis is worse than that of papillary carcinoma and follicular carcinoma, but better than that of undifferentiated carcinoma. The prognosis is worse than papillary carcinoma and follicular carcinoma, but better than undifferentiated carcinoma. Stage I medullary carcinoma of thyroid refers to cancer foci ≤2cm without lymph node and distant metastasis. Stage I is early medullary carcinoma with small cancer foci, which is also confined to the thyroid gland. Generally speaking, it can be treated with radical surgery, iodine 131 treatment, chemotherapy (e.g. cisplatin, vincristine and so on) and other comprehensive treatments, and can have a better curative effect. Patients are advised to communicate with their specialists to choose the appropriate treatment plan according to their condition as well as their personal needs, and regular review is required after surgery.