Primary cutaneous endometriosis of the umbilicus
A 29-year-old woman presented with a 1-year history of an umbilical mass, complaining of periodic pain in the umbilical area synchronized with menstruation. She had no history of surgery or abdominal trauma. Examination revealed a firm, 2.2 cm × 1.8 cm, dark-brown mass on her umbilicus [Figure 1a]. Abdominal computed tomography showed an increased density at the umbilicus without connection to any abdominal organs. Histopathological examination showed multiple endometrial glandular structures surrounded by cellular endometrial-type stroma in the dermis [Figure 1b]. Based on these findings, the umbilical lesion was diagnosed as primary cutaneous endometriosis and it was removed by complete surgical excision.