Fine needle aspiration biopsy is an important tool to determine the benignity or malignancy of thyroid nodules. The National Cancer Institute has developed the Bethesda Reporting System for Thyroid Cytopathology specification, which classifies diagnostic findings into the following 6 grades:
- Grade I, undiagnosable or unsatisfactory;
- Grade II, benign lesions;
- Grade III, atypical cellular lesions of unknown significance, or follicular lesions;
- Grade IV, follicular tumor, or suspicious follicular tumor;
- Grade V, suspicious malignant tumor;
- Grade VI, malignant tumor.
If your puncture results show an “indeterminate” nodule, do you need to keep it under observation or have it surgically removed?
“Indeterminate” nodules include grades III and IV as described above.
The doctor needs to consider the “probability” of malignancy before considering further management:
The probability of grade III being malignant is 10% to 30%, and the probability of grade IV being malignant is 25% to 40%. Therefore, patients with grade III and IV should have a repeat puncture biopsy and morphologic and molecular pathologic examination of the puncture specimen. Molecular pathological examination includes BRAF and RAS gene examination.
If the re-puncture result is malignant, the patient is treated as thyroid cancer; if non-malignant, grade III patients may have ultrasound follow-up; in grade IV patients, the physician may recommend a lobectomy of the affected gland.
Co-written by: Dr. Wei-Zhao Peng, China-Japan Friendship Hospital