Background
Tumor of the follicular infundibulum is a rare benign adnexal tumor arising from the follicular infundibulum. The histopathology of the tumor is distinctive, which occurs as a platelike dermal nodule with multiple thin connections to the overlying epidermis (see the images below). The tumor usually manifests as a single lesion, but an eruptive (multiple) form may occur.
Tumor of the follicular infundibulum shows a platelike dermal tumor with anastomosing islands and cords with connections to the overlying epidermis and horn cysts (hematoxylin and eosin stain, 40X magnification).
Tumor of the follicular infundibulum shows epidermal connections, horn cysts, and anastomosing islands (hematoxylin and eosin stain, 100X magnification).
Tumor of the follicular infundibulum shows epidermal connections, peripheral palisading, and horn cyst (hematoxylin and eosin stain, 400X magnification).