Immunohistochemistry of adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma

Objectives: The aim of the present study was to examine the immunoreactivity of a sufficient number of adenoid cystic carcinoma (AdCC) and polymorphous low-grade adenocarcinoma (PLGA) of the oral cavity to epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA) with the special goal of assessing the ability of these markers to distinguish AdCC from PLGA. The biologic behavior of these malignant tumors is different and the use of these two markers in differential diagnosis between these two tumors can prove to be useful when the histological features on routine hematoxylin and eosin are equivocal or less than classic. Methods:Four-teen cases of AdCC, 10 cases of PLGA and 5 normal minor salivary glands routinely processed, formalin-fixed, paraffin-embedded samples were retrieved from the files of the Department of Oral Medicine and Oral Pathology at the School of Dentistry of Thessaloniki, and were retrospectively studied using the streptavidin-biotin-complex method for the detection of EMA and CEA.Monoclonal rabbit anti-EMA( Novocastra, Newcastle Upon Tune, UK) and polyclonal rabbit anti-CEA (DAKO,Glostrup, Denmark) were used. The staining patterns were classified as luminal when the staining was present in the luminal border of acinar, ductal and tubular structures, as diffuse when part or the whole cytoplasm was uniformally stained, and as granular when tiny dark granules were present in the cytoplasm.Immunoreactivity was scored on a scale of 0 to 4+ according to the approximate percentage of reactive cells. Results: The expression patterns of EMA and CEA in AdCC and PLGA were similar. The average score of reactive cells for both markers was 1.2+ in AdCC and 1.1+ for EMA and 1+ for CEA in PLGA. Conclusion: The results of this study suggest that the immunostaining of AdCC and PLGA with EMA and CEA could not offer and adjunctive aid in differential diagnosis between these two tumors.