Immunohistochemical Expression of BCL-2 Across Histopathological Types of Benign and Malignant Salivary Gland Tumours: A Cross-Sectional Study

Open Access

Abstract

Background: Salivary gland tumours comprise a heterogeneous group of neoplasms with considerable variation in histopathological features and biological behaviour. B-cell lymphoma-2 (BCL-2) is an anti-apoptotic protein that has shown variable expression across different salivary gland tumour types. Objective: The study was conducted to evaluate BCL-2 immunohistochemical expression across histopathological types of benign and malignant salivary gland tumours and to compare its expression between the two biological groups. Methods & Materials: This prospective cross-sectional analytical study was conducted from January 2019 to December 2020 at Sir Salimullah Medical College and Mitford Hospital, Dhaka, Bangladesh. A total of 55 histopathologically diagnosed salivary gland tumours, comprising 33 benign and 22 malignant cases, were included. BCL-2 immunohistochemistry was performed using monoclonal mouse anti-human BCL-2 antibody, clone 124. Expression was assessed as the percentage of immunoreactive neoplastic cells, and a 5% cut-off was used to categorize positive expression. Data were analysed using SPSS version 22, with a p value <.05 considered statistically significant. Results: Positive BCL-2 expression was observed in 29 (52.7%) tumours. Positivity was detected in 12 of 33 benign tumours (36.4%) and 17 of 22 malignant tumours (77.3%). Mean BCL-2 expression was significantly higher in malignant tumours than in benign tumours (34.00 ± 30.02% vs. 4.48 ± 5.29%; p = .001). Among malignant tumours, adenoid cystic carcinoma showed the highest mean expression (67.57 ± 15.38%) with positivity in all 7 cases, followed by mucoepidermoid carcinoma (21.15 ± 20.74%), with 10 of 13 cases (76.9%) positive. Both salivary duct carcinomas were negative. Mean BCL-2 expression differed significantly among malignant histopathological subtypes (p = .001). No significant difference was observed across low-, intermediate-, and high-grade mucoepidermoid carcinomas (p = .897). Conclusion: BCL-2 expression was higher in malignant than benign salivary gland tumours and varied substantially across histopathological types. The highest expression was observed in adenoid cystic carcinoma, while no significant association was found with mucoepidermoid carcinoma grade.