Macrofollicular variant of papillary carcinoma, a potential diagnostic pitfall: A report of two cases including a review of literature
A 55-year-old woman presented with a clinical history of hyperparathyroidism. An ultrasound of the thyroid gland revealed a right-sided 2.9 cm mixed echogenic nodule and a 0.6 cm isthmic nodule containing fine internal calcifications.\nAn ultrasound guided FNA of the right lobe was performed. Air dried smears were stained with Diff-Quik and ethanol fixed smears with Papanicolaou stain. The Diff-Quik smears showed abundant thin colloid and predominantly benign-appearing follicular cells arranged in monolayered pattern. However, other areas showed enlarged round to ovoid follicular cells with nuclear crowding and rare grooves []. Few follicular cells with occasional small nucleoli were also present []. No intranuclear inclusions were identified. Occasional multinucleated giant cells were present. The final diagnosis was atypia of undetermined significance (AUS). Although the Bethesda Recommendation for AUS is repeat FNA after a period of observation, based on the clinical presentation of patient and imaging studies, a total thyroidectomy was performed. The right lobe showed a 2.2 cm encapsulated nodule and two smaller ill-defined white firm nodules measuring 0.3 cm and 0.5 cm. No tumor was seen in the left lobe. Histologic sections from the 2.2 cm right lobe revealed a well-encapsulated tumor composed of colloid-filled macrofollicles occupying more than 50% of the nodule and admixed with smaller follicles. The epithelium of both small and large follicles showed nuclear overlapping, fine chromatin pattern, small eccentrically located nucleoli and few nuclear grooves. No intranuclear inclusions were identified. Capsular or vascular invasion was not identified. Immunohistochemical stain for HBME-1 was positive. The remaining two smaller nodules showed classic micropapillary thyroid carcinoma.