Histopathological and Immunohistochemical Spectrum with Evaluation of Ki-67 Labelling Index on various Thyroid neoplasms.

Abstract

Background: Thyroid lesions encompass a wide spectrum ranging from non-neoplastic conditions to benign and malignant neoplasms. Differentiating these entities, especially follicular patterned lesions, remains a diagnostic challenge. Ki-67, a cellular proliferation marker, has emerged as a useful adjunct in evaluating tumor behavior.

Aim: To analyze the histopathological spectrum of thyroid lesions and to evaluate the role of Ki-67 labelling index in their differentiation.

Materials and Methods: This cross-sectional study included 157 surgically resected thyroid specimens over a period of 5 years (2015–2020). Histopathological examination was performed using hematoxylin and eosin staining. Immunohistochemical analysis of Ki-67 was carried out in 40 selected cases. The Ki-67 labelling index was calculated and statistically analyzed using Chi-square test.

Results: Out of 157 cases, 95 (60.5%) were non-neoplastic and 62 (39.5%) were neoplastic.

Among neoplastic lesions, 18 (11.5%) were benign, 5 (3.2%) were borderline follicular patterned tumors, and 39 (24.8%) were malignant. Papillary thyroid carcinoma was the most common malignancy (80%). Ki-67 expression was absent in non-neoplastic lesions, low in benign tumors (≤3%), and significantly higher in malignant tumors (>3–5%). A statistically significant difference (p<0.05) was observed between benign and malignant lesions.

Conclusion: Ki-67 labelling index is a useful adjunct marker in distinguishing benign from malignant thyroid lesions and plays a significant role in evaluating follicular patterned tumors.