Umbilical Lesions: A Cluster of Known Unknowns and Unknown Unknowns.

Umbilical lesions are rare, but it is important to cautiously inspect and investigate every umbilical nodule or growth to rule out the possibility of embryological remnant and associated congenital anomaly in infants and children and hidden malignancy in adults. Certain umbilical anomalies can be expected in association with certain syndromes (i.e., known unknowns), and at times can be identified during prenatal screening, while others are simply unforeseeable conditions that may arise unexpectedly (i.e., unknown unknowns). Umbilical lesions can be diagnosed on careful clinical and histopathological evaluation. Benign tumours are much more common than metastatic deposits. Certain lesions such as umbilical granuloma can be managed conservatively, while exomphalos and complicated umbilical hernia require urgent surgical intervention. This review article will help to elucidate the spectrum of umbilical lesions, with special emphasis on the importance of proper evaluation of often neglected, but clinically important entities.