Cytomorphological Diagnosis of Primary Umbilical Endometriosis (Villar’s Nodule)

Abstract Primary umbilical endometriosis (PUE), also known as Villar’s nodule, is a rare form of extragenital endometriosis occurring spontaneously without prior abdominal surgery. It accounts for 0.5%–1% of all extragenital endometriosis cases. Due to its rarity and variable presentation, PUE is frequently misdiagnosed as other common umbilical pathologies. We report the case of a 46-year-old multiparous woman with no prior surgical history who presented with a progressively enlarging, pigmented, tender umbilical nodule associated with cyclical pain during menstruation over 7–8 months. Ultrasonography demonstrated a lobulated hypoechoic, hypervascular lesion. Fine-needle aspiration cytology (FNAC) was performed as the primary diagnostic investigation, revealing the characteristic cytological triad of endometrial glandular epithelial cells, stromal fragments, and hemosiderin-laden macrophages against the hemorrhagic background – establishing a preoperative cytodiagnosis of umbilical endometriosis. This was subsequently confirmed on histopathology following wide local excision. This case underscores FNAC as a minimally invasive, cost-effective, and reliable first-line diagnostic tool for PUE. Recognition of its distinctive cytomorphological features is crucial for accurate preoperative diagnosis, optimal surgical planning, and avoidance of misdiagnosis. Histopathology remains the gold standard for definitive confirmation.