Metastases are groups of cells that have detached from the tumor and traveled to distant organs, where they have started to grow and to form new nodules. They can therefore come from a tumor that arises in the colon, breast or lung, for example, and then reach other organs, such as the liver, bone or brain, where they continue to grow.
If metastases appear, they can appear at any time, FIGURE 3:
- in the majority of cases, they appear some time after surgery on the tumor from which they have come (primary tumor);
- sometimes, they appear at the same time as the primary tumor;
- in other cases, they may even appear before the primary tumor is detected.
Each primary tumor has preferential sites to which it spreads metastases.
| PRIMARY TUMOR | MOST FREQUENT SITES OF METASTASES |
|---|---|
| Breast | lymph nodes, skin, lung, bone, liver |
| Lung | lymph nodes, opposite lung, bone, liver, brain, adrenal gland |
| colon | liver, peritoneum, lymph nodes, lung |
| rectum | liver, lung, peritoneum, lymph nodes, bone |
| Pancreas | liver, peritoneum, lymph nodes |
| stomach | liver, peritoneum, lymph nodes, lung, bone |
| ovary | peritoneum, lymph nodes |
| uterus | lymph nodes, lung, liver |
| kidney | lymph nodes, lung, bone, brain |
| Bladder | lymph nodes, lung, bone, liver |
| prostate | bone, lymph nodes, brain, lung |
Therefore, a breast tumor never metastasizes to the colon, and vice versa. A prostate tumor never goes to the stomach, and vice versa.
The reasons for these preferences and incompatibilities is not known. However, it is important to know which sites are most likely to be involved, as this helps to guide our investigations for the staging and follow-up of tumors.