Median raphe cysts: A clinico-pathologic and immunohistochemical study of 52 cases

Background: Median raphe cysts (MRC) are epithelial-lined cystic lesions of the genital area that do not communicate with the urethra or the overlying epidermis. Immunohis-tochemically, MRC show positivity for cytokeratin (CK) 5-6, CK 7, carcinoembryonic antigen, p63 and uroplakin III (URO III). GATA3 and human milk fat globulin 1 (HMFG1) are immunohistochemical markers that have been not previously studied in MRC.Methods: We conducted a study of 52 patients diagnosed with MRC in the Pathol-ogy Departments of eight hospitals between 1990 and 2016. The monoclonal antibodies used were CK5-6, CK7, CK20, URO III, p63, GATA3, and HMFG1. HMFG1 was studied in five cases of apocrine hidrocystomas and compared with five cases of MRC from our series.Results: CK 5-6, CK7, and p63 expression showed strong positivity in the urothelial epithelium of 48 cases. CK20 was focally positive in areas of mucinous differentiation in three cases. GATA3 showed intense nuclear staining in 30 cases. HMFG1 was pos-itive in three cases of MRC and in three cases of apocrine hidrocystoma.Conclusion: Positivity of GATA3 and CK7 in MRC supports the urothelial origin of these cysts. We found no differences in HMFG1 expression between MRC and apo-crine hidrocystomas.