What is your diagnosis?

Histopathological examination of the umbilical nodule revealed plenty of endometrial glands surrounded by compact stroma and intervening hemorrhage, confirming the diagnosis of umbilical endometriosis (PUE) ( Figure 3 ). This was a rare case of Villar’s nodule or PUE without concomitant pelvic endometriosis and in the absence of previous pelvic surgery. PUE is extremely rare, making up 0.5-1% of all ectopic endometriosis cases ( 1 ). Extension of the endometrial cells to the umbilicus via the round ligament or the omphalo-mesenteric canal may explain the occurrence of PUE. Hematogenous or lymphatic transport of the endometrial cells is another possible mechanism that supports the existence of PUE ( 2 ). PUE usually presents around 35-40 years of age. Clinical presentation includes a bluish-purple, firm, umbilical swelling or nodule with associated cyclical pain. Patients can even show catamenial bleeding from the umbilicus concomitantly with the menstrual cycle ( 3 ). Diagnosis is suspected when there is a typical history of an increase in pain/bleeding through the nodule at the time of menstruation. However, diagnosis can be confirmed only by histopathological examination ( 1 , 2 ). Imaging modalities, such as ultrasound, MRI, or computed tomography scan are not superior in terms of sensitivity to the clinical scenario and examination findings ( 4 ). However, imaging can help assess the anatomical relationship of the nodule with the surrounding tissues and to rule out other differential diagnosis of umbilical lesions, like a desmoid tumor, lipoma, Sister Mary Joseph’s nodule, teratoma, trichobezoars, umbilical concretions, and hernia, for example ( 5 ). Imaging can also help to investigate the anatomical relationships of the nodule with the surrounding tissues ( 5 ). Surgery remains the mainstay of treatment. Medical management using progestins, danazol, and/or gonadotrophin releasing hormone agonists may be tried, but recurrence rates are high ( 5 ). Radical omphalectomy is the most frequently performed surgery for umbilical endometriosis. This involves the removal of the umbilicus with the nodule along with plastic reconstruction. Partial omphalectomy is local resection of the endometrial nodule with umbilical sparing. It is important to ensure disease-free margins of at least 3 mm to prevent local recurrences. Sometimes a deep-seated nodule may also necessitate removal of the underlying rectus sheath, which may require anatomical repair or mesh placement.