Differential diagnostic significance of HBME-1, CK19 and S100 in various thyroid lesions

Objective: Due several overlapping histomorphological features and pitfalls in thyroid pathology, there is need to establish a panel of immunomarkers that would aid in proper diagnosis. This study was carried out to investigate the ability of HBME-1, CK19, and S100 in differentiating between hyperplastic, benign and malignant thyroid lesions. Materials and Methods: Immunohistochemical analysis of 60 thyroidectomy specimens (10 hyperplastic nodules, 14 follicular adenomas and 36 malignant thyroid neoplasms) was carried out. The extent and intensity of HBME-1, CK19, and S100 immunoreactivity was assessed in each case. Results: HBME-1 positivity was noted in 86.1% of malignant cases while the majority of the benign lesions were negative. Diffuse strong CK19 positivity was documented in 27/31 papillary carcinoma whereas all cases of follicular carcinoma and medullary carcinoma were negative. Most of the hyperplastic nodules and follicular adenomas were also CK19 negative, although focal weak staining was noted in a few cases. S100 was positive only in medullary carcinoma. HBME-1 was most sensitive (86.1%) and specific (87.5%) in distinguishing between benign and malignant thyroid lesions. The diagnostic accuracy was further increased when HBME-1 was used simultaneously with CK19/S100/CK19+S100. The sequential use of HBME-1 and CK19 also proved beneficial in discriminating between the various follicular-patterned thyroid lesions. Conclusion: HBME-1 immunolabeling suggests malignancy, whereas strong diffuse CK19 positivity substantiates papillary differentiation. The utilization of these markers (alone or in combination) along with histomorphological evaluation is helpful in the differential diagnosis. S100 has minimal utility in this regard.