Differentiating pagetoid Bowen disease from Paget disease on the nipple-areola complex: Two unique, challenging cases

Pagetoid Bowen disease is a subtype of Bowen disease that accounts for 5% of Bowen disease. It is extremely rare for Bowen disease to appear on the nipple-areola complex, with only seven cases described in the previous literature. Of those seven cases, only one was of the pagetoid subtype. We report two cases of pagetoid Bowen disease on this location, one of them being the first case of pagetoid Bowen disease affecting the nipple reported to date. On this location, it is crucial to perform a meticulous differential diagnosis to rule out Paget disease, because of its contrasting therapeutic and prognostic implications. In order to do this, clinical and histopathological aspects must be considered. From a clinical point of view, previous literature has stated that nipple involvement can be a clue that points to Paget disease. However, one of our cases shows that this is not always true. Regarding histopathological analysis, a complete excision of the tumor might be necessary to observe clear features of Bowen disease, such as full-thickness atypia of the epidermis and intercellular bridges. An immunohistochemical panel comprising carcinoembryonic antigen, gross cystic disease fluid protein, epithelial membrane antigen, p63, CK34betaE12, periodic acid-Schiff, estrogen receptor, and progesterone receptor can be decisive in complicated cases.