HBME-1 and CD15 immunocytochemistry in the follicular variant of thyroid papillary carcinoma

Papillary carcinoma is the most common thyroid malignancy. As the cytological diagnosis of papillary carcinoma is not difficult in patients with the usual type of lesion, fine-needle aspiration (FNA) cytology is an effective method for preoperative evaluation. However, this modality is often ineffective in identifying the follicular variant of papillary thyroid carcinoma (FVPTC) due to its similarity to other follicular lesions and the incompleteness of typical nuclear features. Therefore, we investigated the expression of immunocytochemical markers of papillary carcinoma in cytological specimens of FVPTC and evaluated their utilities. The immunoreactivity of HBME-1 and CD15 was investigated using 50 imprint smear cytological specimens obtained from thyroid lesions, including 13 FVPTC. The sensitivity and specificity of HBME-1 for FVPTC were 92% and 89%, respectively, while those of CD15 were 23% and 100%, respectively. In conclusion, HBME-1 is a sensitive marker of papillary carcinoma, including both usual type and FVPTC, in cytological specimens. Therefore, using HBME-1 immunocytochemistry in FNA cytology will lead to reduction of the incidence of false-negative diagnoses of FVPTC. Although CD15 is apparently inferior in terms of sensitivity for FVPTC, its excellent specificity will support the definitive diagnosis of thyroid malignancies, including FVPTC, after screening with HBME-1.