Paget cells contain mucin and cytokeratins which can be used in the diagnosis of EMPD MUC5A2 is found in EMPD of the vulvar and male genitalia regions whereas MUC2 is expressed in perianal EMPD. Loss of MUC5A2 can indicate an invasive spread. Immunohistochemistry (IHC) can be used to determine whether EMPD is either primary or secondary. Primary EMPD tests positive for CK7 but negative for CK20, whereas secondary is positive for both. Lack of positivity for hormone receptors and HER2 protein is overexpressed meaning that the cells are dividing rapidly and can be indicate an aggressive and more recurrent disease.