The presence of diffuse lesions in the other half of the thyroid cancer after hemicolectomy usually requires consideration of the possibility of Hashimoto’s thyroiditis, which needs to be treated as early as possible. Thyroid cancer after hemicolectomy causes different degrees of immune system damage, which stimulates the remaining thyroid gland to develop chronic inflammation, which also belongs to the immune system disorders, and is a common cause of diffuse changes on imaging. For Hashimoto’s thyroiditis after thyroid cancer surgery, first of all, we need to carry out tumor marker examination to determine whether there is metastasis and recurrence of cancer, and at the same time, we need to cooperate with the detection of thyroglobulin antibody and thyroid peroxidase antibody to further clarify the diagnosis, and we need to regulate the function of thyroid gland through thyroxine supplementation at the earliest possible time, and we can also consider the second surgery. If diffuse changes such as Hashimoto’s thyroiditis occur during the recovery process of thyroid cancer, it is recommended to improve the examination and treatment as early as possible. If the use of hormone medication is needed, it is recommended to use the medication cautiously under the guidance of doctor.