Brown Umbilical Nodule: A Case of Primary Cutaneous Endometriosis

This unique case demonstrates primary cutaneous endometriosis in the umbilicus of a female patient. Cutaneous endometriosis can be classified as primary or secondary. Primary cutaneous endometriosis is rarer and has an unclear etiology, developing seemingly spontaneously without history of surgical interventions. Secondary cutaneous endometriosis typically arises within surgical scars following abdominal operations, which is believed to be a result of iatrogenic implantation of endometrial cells. Definitive treatment involves surgery. This case highlights the importance of considering cutaneous endometriosis in the differential diagnosis of a female patient with painful and intermittently hemorrhagic skin nodules.