Syringocystadenoma Papilliferum

Syringocystadenoma papilliferum (SP) is a well-delineated lesion composed of interconnected papillary fronds and duct-like structures. Typically, the epidermis will show one or more cystic invaginations (right) which extend downward into the dermis. This feature can be helpful in distinguishing SP from hidrandeoma papilliferum (helpful hint: Syringocystadenoma papilliferum opens up to the Surface, whereas Hidradenoma papilliferum does not maintain a connection to the epidermis and Hides in the dermis). Near the surface, the invaginations are lined by squamous epithelium, which gradually transitions to a bi-layered epithelium composed of cuboidal and columnar cells.