Immunohistochemical Expression of BCL-2 in Malignant Salivary Gland Tumors

Abstract

Background: Malignant salivary gland tumors (MSGTs) consist of a heterogeneous group of neoplasms with complex clinicopathological features and biological behaviors. The purpose of this study was to determine the expression of Bcl-2 antiapoptotic protein in mucoepidermoid carcinoma (MEC), adenoid cystic carcinoma (ADCC), acinic cell carcinoma (ACC) and polymorphous low-grade adenocarcinoma (PLGA) of salivary glands and to find out its association with different grades of these tumors.
 Material and Methods: This descriptive study included 55 cases of MSGTs. Tissue sections were stained with routine hematoxylin and eosin stain as well as Bcl-2 immunostain. MSGTs were graded as low grade (Low grade MEC, ACC, PLGA, and tubular pattern of ADCC), intermediate grade (cribriform pattern of ADCC, and intermediate grade of MEC) and high grade (high grade of MEC and solid pattern of ADCC) tumors on H&E sections. Bcl-2 expression was scored as ‘negative’ (<5% of neoplastic cells), ‘1’ (5-19% of neoplastic cells), ‘2’ (20-49% of neoplastic cells), and ‘3’ (>50% of neoplastic cells), respectively.
 Results: MSGTs most commonly involved the parotid gland (52.7%), while ADCC (40%) and MEC (38.2%) were the most common tumors. Expression of Bcl-2 was strongly positive in 56.4% cases of MSGTs which included ADCC (71%), MEC (19.4%) and ACC (9.7%), respectively. A significant association was found between Bcl-2 staining and types of MSGTs i.e., MEC, ADCC, ACC (P = .001) as well as between Bcl-2 staining and grades of MSGTs (P = .013).
 Conclusions: Bcl-2 protein is expressed in malignant salivary gland tumors. Its expression maybe helpful in grading small biopsies, predicting behavior, and planning targeted therapy of MSGTs.