A malignant nodule generally means cancer because cancer cells can be found in the nodule. Usually, malignant nodules require surgery, such as malignant nodules in the breast or malignant nodules in the thyroid, when the diagnosis is clear or when malignancy is highly suspected. In the case of malignant thyroid nodules, both thyroid glands need to be removed at the same time and the lymph nodes in the area need to be cleared. In the case of malignant nodules in the breast, a modified radical mastectomy is required, and the lymph nodes in the armpit should be cleared and chemotherapy should be administered after surgery. Malignant nodules are classified as hypofractionated, moderately differentiated or highly differentiated depending on the malignancy of the tumor, the lower the differentiation, the higher the malignancy.