Utility of p63 and p40 in Distinguishing Polymorphous Adenocarcinoma and Adenoid Cystic Carcinoma

OBJECTIVE: Adenoid cystic carcinoma and polymorphous adenocarcinoma are primarily the tumor of minor salivary glands. Both show certain morphological similarities, which limit their proper diagnosis in settings where there are obscuring factors and limited biopsy material. However, there is a considerable difference in treatment and prognosis, which raises the need to distinguish these two entities. In this study, we discuss the utility of two immunohistochemical stains, p63 and p40, in different combinations for distinguishing polymorphous adenocarcinoma from adenoid cystic carcinoma. MATERIALS AND METHODS: Two immunohistochemical stains, p63 and p40, were performed on 47 cases of adenoid cystic carcinoma and 23 cases of polymorphous adenocarcinoma. RESULTS: 36 out of 47 cases of adenoid cystic carcinoma showed p63+ve/p40+ve immunoprofile, followed by p63-ve/p40-ve immunoprofile, which is seen in10 cases of adenoid cystic carcinoma. However, 22 out of 23 cases of polymorphous adenocarcinoma displayed p63+ve/p40-ve immunoprofile. p63-ve/p40+ve is the least frequent observed immunoprofile, which is seen in only one case of adenoid cystic carcinoma. CONCLUSION: On combining all possible immunoprofile combinations, p63+ve/p40-ve immunoprofile appears to be the most sensitive profile for distinguishing polymorphous adenocarcinoma from adenoid cystic carcinoma.