Primary Cutaneous Endometriosis of the Umbilicus: A Diagnostic Challenge

Umbilical endometriosis, or Villar's nodule, is a rare form of cutaneous endometriosis in which ectopic endometrial tissue involves the umbilical skin. It may occur without any history of abdominal or gynaecological surgery, making diagnosis difficult and leading to misdiagnosis as more common umbilical lesions. We describe a 31-year-old woman with a 2-year history of an enlarging umbilical lesion associated with intermittent swelling, discomfort, and persistent moisture, with flares around menstruation. She was treated repeatedly in primary care for presumed infection or umbilical granuloma using topical antifungals and antibiotics, without sustained improvement. Examination revealed a polypoid, lobulated violaceous-brown nodule within the umbilicus. Ultrasound demonstrated a vascular pedunculated nodule confined to the anterior abdominal wall. Punch biopsy showed endometrial-type glands and stroma in the dermis, and immunohistochemistry confirmed cutaneous endometriosis. She was referred to gynaecology for evaluation of possible pelvic endometriosis and to plastic surgery to consider surgical excision and umbilical reconstruction; definitive surgery is pending at the time of writing. This case highlights umbilical endometriosis as an important differential diagnosis in women presenting with umbilical nodules and cyclical symptoms and underscores the role of histopathology in distinguishing Villar's nodule from malignant or metastatic umbilical lesions.