3 ways in which tumors can spread from a primary the site to bone

1. Direct Extension

   1. Direct invasion into a bone may occur from a soft tissue tumor lying adjacent to or near the bone.

   2. An example is carcinoma of the uterus which is known to cause direct extension to the iliac bones

2. Lymphatic Dissemination

   1. This is uncommon. It is thought that the absence of lymphatic channels in bone marrow is the reason for the relatively low incidence of lymphatic seeding of bone.

3. Hematogenous Dissemination

   1. Spread through blood vessels, particularly the veins, is the most common pathway for tumor emboli. The three most commonly seeded in this manner are the lungs, liver, and the axial skeleton.

   2. Batson’s Venous Plexus are valveless veins where blood can reflux when intrathoracic and intra-abdominal increases. Batson’s plexus also provides a series of venous passageways by which cancer cells can be directly seeded into bones.

Category: Tumors Revision