Sister Mary Joseph's nodule: Three case reports.

Background: An umbilical metastatic lesion is called 'Sister Mary Joseph's nodule'. It is an uncommon clinical or radiographic finding, and it is rare as the first sign of a malignant disease.

Methods: We report three cases of Sister Mary Joseph's nodule. In the three cases presented, the primary tumor was an adenocarcinona of the sigmoid colon, a carcinoma of the bladder, and an adenocarcinoma of the gallbladder, respectively.

Conclusions: The differential diagnosis of an umbilical lesion should always include metastatic disease apart from benign lesions and primary neoplasms.