The ultrasonic appearance of a thyroid nodule does not reliably differentiate a benign thyroid lesion and cancer.
However, there are some ultrasonographic signs that are thought to indicate increased risk of cancer--
1.Central intra-nodular vascularity
2. Incomplete/absent halo
3. Hypoechoic nodules
4. Irregular margins
6. Documented enlargement of a nodule
7. predominantly solid composition
One must remember that these are only certain guidelines (not universally accepted)
Certainly the next step most would recommend in your case would be a FNAC(Fine Needle Aspiration Cytology) of the mass(whatever the result of Thyroid function tests).
MB BS, MS, FRCS(Edinburgh)