Clinical features:
(1) The color may be any combination of blue, red or brown.
(2) The nodule may be tender or painful. It may enlarge during menstruation.
(3) The lesion may be cystic or solid.
(4) A cutaneous fistula may occur and drain blood during menstruation.
(5) The woman may have a history of endometriosis.
Common locations:
(1) umbilicus
(2) surgical scars (Bartholin cyst surgery, perineal lacerations, Cesarean section site, laparoscopy site, abdominal scar)
(3) vulva or perineum
Surgical excision will show histologic features of endometriosis, with glands, stroma, fibrous tissue, hemosiderin and blood.
Differential diagnosis:
(1) cutaneous metastasis
(2) skin adnexal tumor
(3) epidermoid cyst
(4) lipoma
(5) scar granuloma
