CD15 and CEA expression in thymic epithelial neoplasms

The aim of this study was to evaluate the expression of CD15 and CEA in thymic epithelial neoplasms and assess their correlation with various World Health Organisation (WHO) subclasses of thymic epithelial neoplasms. A total of seventy cases of thymic epithelial neoplasm seen between 1981 and 2001 were retrieved from the archives of the Department of Pathology at Hacettepe University. Hematoxylene and Eosin stained sections were evaluated and reclassified according to the WHO classification. Representative sections from each case were stained for CD15 and CEA by immunohistochemical technique. CD15 was strongly positive in 4 of 5 (80%) WHO type A cases and specifically stained the A component in all of mixed (AB) thymomas. While 3 of 5 (60%) WHO type C cases strongly expressed CD15, none of WHO type B cases demonstrated strong positivity. Strong CEA expression was not seen in any of the cases. Heterogeneous staining pattern (+2) was seen in only WHO type C cases and not in any of type A or B cases. Thus, CD15 expression highly correlates with type A component of thymic epithelial neoplasms. CEA expression on the other hand can be seen in type C thymic epithelial neoplasms.