Abstract

BACKGROUND
The most important feature distinguishing intraductal papilloma (IDP) from papillary carcinoma is the presence of uniform myoepithelial cells (MECs) within the lesion.
METHODS
Immunohistochemistry (IHC) for calponin, smooth muscle myosin heavy chain (SMMHC), cytokeratin 34E12, and p53 were performed on 37 IDP, 4 intraductal papillary carcinomas (IDPCA), 5 microinvasive papillary carcinomas, and 5 invasive papillary carcinomas (IPCA), respectively.
RESULTS
The mean age of the patients was 43 (43.3+/-11.6) years. Cytokeratin 34E12 was expressed in epithelial cells (84%) as well as in MECs (23%) of IDP. The expression of SMMHC was significantly reduced in the intraductal and invasive papillary carcinoma (p=0.001). The expression of calponin was also significantly reduced (P<0.001) as IDP 95%, IDPCA 76%, microinvasive papillary carcinoma 39%, and IPCA 8%, respectively. p53 over-expression was noted in 3 (one IDP and two IPCA) of 51 cases.
CONCLUSIONS
Because MECs were significantly reduced with malignant progression, calponin and SMMHC were very useful markers for differentiating between benign and malignancy in the papillary neoplasm. Calponin was more sensitive than SMMHC and was an excellent ancillary test for assessing MECs and for detecting microinvasion.

• Keywords: Thymus glandNeoplasms;Immunohistochemistry;World Health Organization;Histological classification;