Follicular adenocarcinoma of the thyroid gland requires routine pathological examination, and if peritoneal infiltration is found in the specimen section, while no vascular infiltration can be judged as microinfiltration. Follicular adenocarcinoma of the thyroid is a malignant tumor of follicular cell origin of the thyroid gland, which lacks the characteristic changes of the nucleus of papillary thyroid carcinoma, and the diagnosis is mainly based on the biological characteristics of peritoneal and vascular infiltration as well as the tendency to metastasize in the routine pathological examination. According to pathological examination, thyroid follicular adenocarcinoma can be classified into micro-infiltrating type, intraperitoneal vascular infiltrating type, and extensively infiltrating type. Microinvasive type refers to the presence of peritoneal infiltration, but without blood vessels and extraperitoneal infiltration of cervical muscles and nerves. Puncture biopsy as well as intraoperative rapid frozen section, even 3~5 sections of conventional pathology may not show evidence of peripheral and vascular infiltration, and multiple pieces of tissues need to be taken around the periphery of the periphery for embedded section observation. Microinvasive carcinoma belongs to malignant tumors, but its prognosis is better than that of extensive infiltrative, and patients are recommended to consult with specialists and actively follow the medical advice for treatment.