Ultimobranchial Body Remnants (Solid Cell Nests) as a Pitfall in Thyroid Pathology

We report the history of a pitfall in thyroid histopathology of a 47-yr-old man with a euthyroid nodular goiter involving the right lobe. The ultrasound-guided fineneedle aspiration of the dominant (3 cm) nodule, showing benign-appearing follicular cells, colloid, and scattered Hurthle cells, was consistent with a benign hyperplastic nodule (1). Because the left lobe had not shown evidence of nodular disease, the patient was submitted to a right lobectomy. The pathologist described a heavy lymphoplasmacyticbackgroundwithoccasionalgerminalcenter formation, as observed in Hashimoto thyroiditis, and a microscopic ( 1cm) follicularproliferationofepithelial thyroidcellswhose nucleidisplayedmembrane irregularityandchromatinclearing with occasional grooves. Thus, a histological report of a follicular variant of papillary microcarcinoma was issued. The patient underwent a completion thyroidectomy at the Federico II UniversityofNaples.At thatoccasion, thecompletesetofslides from both surgeries was reviewed by expert pathologists in the field of thyroid disease.