A case of papillary microcarcinoma of the thyroid with abundant colloid (masquerading as colloid goiter with papillary hyperplasia): Cytological evaluation with histopathological correlation

Papillary thyroid carcinoma (PTC) is the most common malignant neoplasm of the thyroid. On fine-needle aspiration (FNA) cytology smears of conventional PTC, the background usually shows scanty, bubble gum-like colloid. But the macrofollicular variant and papillary microcarcinoma reveals abundant thin colloid in the background. We report a case of papillary carcinoma of thyroid in a 37-year-old female with abundant thin colloid, obscuring the nuclear morphology in many clusters, along with the presence of typical nuclear features within occasional clusters in FNA cytology and hence, masquerading as colloid goiter with papillary hyperplasia. Histopathological examination of the total thyroidectomy specimen revealed papillary microcarcinomatous focus in a background of nodular hyperplasia. The differential diagnosis of PTC should be entertained even in colloid-rich FNA smears if the typical nuclear features are present. Hence, a meticulous search for any fragment with nuclear features of PTC is mandatory before labeling the smears as benign nodular hyperplasia.