What does heterogeneous mean when it comes to a thyroid nodule?

It means irregular: Heterogeneous is the opposite of homogenous. Any thyroid nodule which is irregular and over 1cm in size needs to be investigated further. This may need a biopsy especially if it is growing or has increased in size over a period of 3 months. You should have your doctor guide you or send you to an endocrinologist. For a second opinion and further advice.