A Mechanism for a Sign: The Answer Comes from The Embryo
The periumbilical and umbilical area is a common view during the physical examination , usually just a point to change direction to the rest of the abdomen.
We can see here benign conditions such as a hernia or infection, but also, in patients with a previous diagnosis of a malignant tumor, it is possible to detect the presence of a metastasis inside or around the navel, the so called Sister Mary Joseph´s nodule.
How these cells arrive in this anatomical area?
The answer is through the umbilical vein or more precisely, the round ligament, an embryonic remnant of this vein. The neoplastic cells can take a retrograde path from the abdomen to the navel and around, what is a sign of cancer dissemination. The incidence of metastatic tumours in the umbilical region that are secondary to intra-abdominal tumours is very low.
During the embryonic development the umbilical vein connects the placenta with the vena cava, through the left branch of the portal vein. In the adult there is another anatomical structure, the paraumbilical vein, that connect the abdominal wall around the periumbilical area with the left branch of the portal vein.
The umbilical and periumbilical area is visible during the physical examination, but only if you look at it. The sheet, the trousers or a bandage covering a scar, could be in the origin of a diagnostic error. Moreover, the low incidence of this problem may explain the situations of no detection, because your mind can be thought in the more common findings in the liver or the rest of the abdomen.
You have to be methodical always. Try to be alert investing the proper time. Don´t look partially, be sure to examine the whole anatomical region.