Primary umbilical endometriosis: a rare variant of extragenital endometriosis.

Endometriosis is defined as the presence of extra-uterine endometrial tissue. The prevalence rate of umbilical endometriosis ranges from 0.5 to 1.0% of all patients with extragenital endometriosis. In this report, we present a case of primary umbilical endometriosis to highlight the challenges encountered during diagnosis. A nulliparous 39-year-old woman presented to our department with a 2-year history of a tender, painful and non-reducible, firm umbilical mass that enlarged slowly reaching 2 cm in diameter. She had never been pregnant nor had any abdominal surgery. There was no sequential bleeding. Ultrasound of the umbilical region showed a well defined, oval shaped anechoic area. Histological examination on a cutaneous biopsy concluded umbilical endometriosis. The patient was subsequently referred to a gynecologist and underwent surgery with en bloc excision of the lesion. Generally, umbilical endometriosis presents as a roundish tumuor that can either partly or completely occupy the umbilical scar with intermittent bleeding. Characteristically, the mass increases with the menstrual cycle, becoming more evident and usually harder and is associated with cyclic pain. Its pathogenesis remains uncertain. Clinical diagnosis is difficult, and umbilical endometriosis can be easily confused with other conditions such as benign and malignant tumours. Ultrasound examination is useful, and surgical excision is the treatment of choice. Several cases of malignant transformation have also been described.