The role of immunolocalization of CD57 and GLUT-1 in cell blocks in fine-needle aspiration diagnosis of papillary thyroid carcinoma

BACKGROUND. CD57 (Leu7), a marker for natural killer lymphocytes, and glucose transporter-1 (GLUT-1), a facultative cell surface glucose transport protein, are expressed in a wide spectrum of epithelial malignancies. The usefulness of CD57 and GLUT-1 immunostaining was evaluated as an adjunct to assist in the diagnosis of papillary carcinoma in fine-needle aspirations (FNAs) of the thyroid. METHODS. Immunohistochemical staining for CD57 and GLUT-1 was performed on paraffin-embedded cell blocks of 50 thyroid FNA cases with the following cytologic diagnoses: 1) papillary carcinoma (15 cases); 2) atypical cytology, cannot exclude papillary carcinoma (14 cases); and 3) benign thyroid (21 cases). RESULTS. Fourteen of 15 cases with an unequivocal diagnosis of papillary carcinoma were positive for CD57 and 1 case was negative for CD57. Tissue follow-up confirmed papillary carcinoma in all 15 cases. Of the 14 cases with a diagnosis of atypical cytology, cannot exclude papillary carcinoma, 6 cases were positive for CD57 and subsequent excision confirmed papillary carcinoma in all 6 cases. The remaining 8 cases negative for CD57 included surgically confirmed goiter (5 cases), adenoma (2 cases), and papillary carcinoma (1 case). The follicular cells in all 21 cases with a cytologic diagnosis of benign thyroid were negative for CD57. Histologic follow-up of these cases confirmed the benign cytologic diagnoses. GLUT-1 was negative in all cases. The sensitivity and specificity of CD57 was 91% and 100%, respectively. CONCLUSIONS. CD57 immunostaining is a useful adjunct for the diagnosis of papillary thyroid carcinoma in cell block material. Although negative staining for CD57 does not completely exclude papillary carcinoma, positive staining aids in the accurate diagnosis of malignancy in cytomorphologically equivocal cases. GLUT-1 did not prove to be a useful marker in distinguishing papillary carcinomas.