There is a large hypoechogenic lesion occupying almost the entire left lobe. It could be a nodule at first sight, but there are strong arguments against this possibility. Firstly, the extensive fibrotic changes. Secondly, the irregular, puzzle-like sharp borders of the lesion. Thirdly, which is not demonstrated here, the presence of similar smaller hypoechogenic areas in the right lobe.

To summarize: this lesion is with great probability not a nodule, but the part of the lobe which is influenced by thyroiditis, while the extralesional part with normal echogenicity is not or less influenced by the underlying autoimmune process. FNAC is not mandatory but may be advised from a practical reason: the patient will undergo a lifelong follow-up investigation and has a great chance being investigated in the future by a colleague who is not absolutely familiar with the thyroid. Such colleague may give the diagnosis of a nodular goiter. If we prove that this lesion is benign, such possibly false diagnosis will cause less anxiety for the patient.

This patient underwent surgery, the final histopathology disclosed Hashimoto's thyroiditis, and there wasn't any nodule in the thyroid.