Unless the nodule is an autonomous functioning nodule (rarely malignant), two individual biopsies are required to conclude that a lesion is not cancer. With RFA therapy the tissue is not removed and sent to the pathologist for analysis. After RFA therapy, surveillance ultrasound might identify irregularities within the nodule which could be interpreted as suspicious. This interpretation may prompt further biopsies. Because cytology tissue may look more atypical after RFA treatment assurance of benign tissue is very important prior to therapy.