Two Cases of Hidradenoma Papilliferum

We present two female cases of hidradenoma papilliferum on the vulva. The first case was a 40-year-old woman who recognized a subcutaneous nodule measuring 6 mm on the left of her vulva. The nodule was surgically resected and diagnosed as hidradenoma papilliferum histologically. The second case was a 38-year-old woman with a pink-colored pedunculated tumor measuring 1 cm on the left of her vulva, which often bled because of friction from underwear. The tumor was surgically resected and was also diagnosed as hidradenoma papilliferum histologically. It had previously been thought that hidradenoma papilliferum tumors originate from apocrine sweat glands, but recent studies have suggested that they may be derived from the anogenital mammary-like gland (MLG). The MLG is reported to be immunopositive for both estrogen receptor and progesterone receptor, while the majority of the normal eccrine or apocrine glands are not. Our two cases showed both estrogen receptor and progesterone receptor expression in the columnar cells of the tumor, suggesting that these cases of hidradenoma papilliferum may have been derived from the MLG.