Sister Mary Joseph nodule: a tip of an iceberg.

A Sister Mary Joseph nodule represents a cutaneous metastasis into the umbilicus. This clinical sign of intra-abdominal malignancy is frequently overlooked or misinterpreted by both patients and their physicians. We report 4 patients with a Sister Mary Joseph nodule. The umbilical metastases appeared sonographically as hypoechoic masses with irregular margins and small internal hyperechoic foci. Further evaluation revealed disseminated malignancy, and the umbilical nodule was just "a tip of an iceberg."