Hidradenoma papilliferum, light micrograph (LM) of a section of affected vulva. Hidradenoma papilliferumis a type of benign cystic papillary growth (lower part of image) that occurs on the labia majora of the vulva. It may be also be present on the interlabial folds. These hidradenomas are caused by a nodule of breast tissue that is ectopic, (located away from its normal anatomical location) and are often present at birth. Magnification: x 150 when printed at 10 centimetres wide. Human tissue.