Features Suggestive of Malignant Thyroid Nodules

Fig. 1 Longitudinal ultrasound of the thyroid reveals an ill-defined hypoechoic nodule in the upper pole of the thyroid lobe (between calipers). Note microcalcification (yellow arrow).
Fig. 2 Color Doppler ultrasound of the nodule shows intranodular vascularity (green arrow).

Both pictures illustrate three important findings on ultrasound that are suggestive of malignancy (these are independent risk factors of nonpalpable malignant thyroid nodule):

1. Irregular margin
2. Intranodular vascular spots
3. Microcalcifications

Other Facts:

• Thyroid nodules are increasingly common because widespread use of neck ultrasound
• Management of incidentally detected thyroid nodule is still largely controversial
• When needed, cytological evaluation by fine needle aspiration biopsy (FNA) is the best method to assess thyroid nodule
• Other signs that ones should look for: extracapsular growth and nodal involvement. These are helpful in predicting malignancy.
• Prospective study had shown that size (<1 cm vs. larger), number (solitary vs. multinodular), and echogenicity (hypoechoic vs. iso-hyperechoic) were not different in groups with benign or malignant nodules.
  

Reference:
Papini E, et al. Risk of Malignancy in Nonpalpable Thyroid Nodules: Predictive Value of Ultrasound and Color-Doppler Features. J Clin Endocrinol Metab 2002;87:1941.