Learning Objective
By the end of this section, learners should be able to identify the primary tumors most likely to metastasize to specific organs, understand their preferred routes of spread, and recognize typical radiologic/pathologic features of metastases.
General Principles
- Most carcinomas spread via lymphatics, while most sarcomas spread hematogenously (CLaSH: Carcinoma → Lymphatics, Sarcoma → Hematogenous).
- Exceptions: Four carcinomas spread primarily via the bloodstream:
- Follicular thyroid carcinoma
- Choriocarcinoma
- Renal cell carcinoma
- Hepatocellular carcinoma
- Metastases often appear as multiple lesions, unlike primary tumors, which are usually solitary.
Activity
Metastasis by Organ
| Site of Metastasis | Common Primary Tumors | Notes |
|---|---|---|
| Bone | Prostate, breast >> lung > kidney, colon | Predilection for the axial skeleton. Types of bone metastases: • Blastic: prostate, small cell lung • Mixed: breast • Lytic: kidney, colon, non-small cell lung |
| Liver | Colon > breast >> pancreas, lung, prostate | Metastases are scattered throughout the liver parenchyma. |
| Lung | Colon, breast >> kidney, prostate | Typically involves both lungs. |
| Brain | Lung > breast >> melanoma > colon, prostate | Lesions usually appear at the gray–white matter junction. |
High-Yield Exam Pearls
- Remember CLaSH for carcinoma vs sarcoma spread.
- Bone metastases are blastic for prostate, lytic for kidney/colon.
- Liver metastases commonly arise from colon cancer.
- Brain metastases frequently come from lung cancer, especially at the gray–white matter junction.
