Umbilical endometriosis. Umbilical endometriosis (UE) is attributed to the rare forms of extragenital endometriosis presented in the literature through unique clinical trials or limited series. UE is a very rare condition with an estimated prevalence of <1% of all ectopic endometriosis. The first description of a primary umbilical endometrioma is credited to Villar in 1886, hence the term Villar’s nodule. UE is even more difficult to diagnose due to the extreme lack of clarity in clinical signs. Given the location of the given pathology, a differential diagnosis with other umbilical surgical diseases is necessary. A review of the literature of the last 10 years was generated based on PubMed and Google Scholar research, selecting some specific keywords. Several lesions can occur in the umbilical region, and endometriosis has to be ruled out even in patients without any surgery in their medical history. Surgery is the gold standard treatment for this condition. Considering the multitude of pathologies of the umbilical region that may look similar to EO, this condition must be considered in the differential diagnosis. Radical surgical excision is the preferred treatment aimed at preventing recurrence and reducing the risk of malignant transformation.