Assessment of CD43 expression in adenoid cystic carcinomas, polymorphous low-grade adenocarcinomas, and monomorphic adenomas.

OBJECTIVE: Distinguishing between adenoid cystic carcinoma (ACC), polymorphous low-grade adenocarcinoma (PLGA), and monomorphic adenoma (MA) can occasionally pose a diagnostic challenge. It is of interest to identify a marker that can differentiate between these tumors. CD43 is a sialoglycoprotein that is typically expressed by hematopoietic cells and their derivative neoplasms, although positivity in epithelial tumors has been recently recognized. Our aim was to investigate CD43 immunoreactivity in ACCs, PLGAs, and MAs. STUDY DESIGN: Formalin-fixed paraffin-embedded sections from 40 salivary gland tumors (12 ACCs, 14 PLGAs, and 14 MAs) accessioned from 1989 to 2002 were retrieved from the files at the Department of Pathology, Long Island Jewish Medical Center. Immunohistochemical staining with anti-CD43 monoclonal antibody was performed. RESULTS: Cytoplasmic and membranous immunoreactivity was detected in 12/12 ACCs (100%), 1/14 PLGAs (7.1%), and 3/14 MAs (21.4%). CONCLUSIONS: CD43 appears to be preferentially expressed in salivary gland ACCs compared to PLGAs and MAs. Although the mechanism of this overexpression remains obscure at this time, our results suggest that the use of CD43 immunostaining as an adjunct to histological examination may be helpful in differentiating ACC from its mimics.