The Utility of BSND Immunohistochemistry in the Differential Diagnosis of Oncocytic and Warthin-like Mucoepidermoid Carcinoma of Salivary Gland

BSND is a chloride channel subunit that is expressed in the normal salivary gland. We aimed to validate the utility of BSND immunohistochemistry in the differential diagnosis of oncocytic salivary gland neoplasms.

BSND immunohistochemistry was performed in a retrospective cohort of 93 salivary gland lesions, enriched with tumors with oncocytic features and histologic variants of mucoepidermoid carcinoma (MEC).

All oncocytomas (n = 18) showed diffuse membranous BSND immunopositivity. Warthin tumors (n = 18) were also positive for BSND, but the staining pattern was patchy cytoplasmic and membranous in 10–25% of tumor cells. Using a threshold of 10% BSND-positive cells, all Warthin tumors were positive, while none of Warthin-like MECs or non-MEC salivary tumors were positive. Applying the same 10% positivity criterion, two oncocytic MECs were positive for BSND. The percentage of BSND staining in oncocytic MECs was up to 20%. In contrast, BSND was diffusely positive in oncocytomas with a median percentage of positivity of 95% (range: 40 − 100%). Therefore, a higher threshold of > 20% BSND-positive cells may be considered when differentiating between oncocytoma and oncocytic MEC.

BSND immunohistochemistry is a potentially useful diagnostic marker for salivary gland neoplasms, especially oncocytic and Warthin-like MECs. A threshold of ≥ 10% positivity can differentiate Warthin tumors from Warthin-like MECs, whereas > 20% positivity can be effective for separating oncocytomas from oncocytic MECs.