Clinical presentation: A 55-year-old woman was referred for follow-up investigation. The patient was first diagnosed having hypothyroidism and nodular goiter five years ago. Aspiration cytology resulted in Hashimoto's thyroiditis. Her lesion in the left lobe increased in size, therefore a repeat FNAC was suggested.

Palpation: Both lobes were firm. No nodule could be palpated.

Hormonal investigation: euthyroidism on daily 75 microgram levothyroxine (TSH 1.72 mIU/L).

Ultrasonography revealed a hypoechogenic, inhomogeneous thyroid having small discrete, less hypoechogenic areas. The largest of these lesions was in the lower part of the left lobe and presented halo sign and perilesional blood flow. The size of the lesion was 11x11x13 mm and 17x17x19 mm, in 2011 and in 2016, respectively. The difference means an almost 3.5-fold increase in volume.

Aspiration cytology disclosed Hashimoto's thyroiditis.

Comments.

1. On ultrasound we cannot unequivocally decide whether this lesion is a nodule in a pathological sense or not. The presence of similar smaller areas elsewhere in the thyroid favors the latter while the significant increase in size does the former possibility.
   
2. The histogram value of the lesion is 69.4. It means that although the nodule is more echogenic than the-non-lesional part of the lobe, its echogencity is lower compared with a healthy thyroid. The latter is characterized by a mean histogram value of 82.0. So, the nodule should be grouped among iso/hyperechogenic lesions if the reference tissue is the non-nodular part while should be grouped among moderately hypoechogenic nodules if the reference tissue is the healthy thyroid.