Learning Objectives
Master the Common Metastases and their primary origins. Identify the specific carcinomas that defy the rule of lymphatic spread and understand the characteristic appearance and locations of Bone, Liver, Lung, and Brain metastases.
1. Patterns of Dissemination
A fundamental rule in oncology is that Carcinomas typically spread via lymphatics, while Sarcomas spread hematogenously (through the blood).
| Rule / Mnemonic | Exception: Hematogenous Carcinomas |
|---|---|
| CLaSH Carcinomas = Lymphatics Sarcomas = Hematogenous |
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2. Sites of Metastasis and Primary Origins
Metastatic lesions are more common than primary malignancies in the bone, liver, lung, and brain. They typically present as multiple lesions, whereas primary tumors are often solitary.
| Site | Primary Tumors (In Order) | Notes |
|---|---|---|
| Bone | Prostate, Breast >> Lung > Kidney | Predilection for the axial skeleton. |
| Liver | Colon > Breast >> Pancreas, Lung | Scattered nodules throughout the parenchyma. |
| Lung | Colon, Breast >> Kidney | “Cannonball” metastases; involves both lungs. |
| Brain | Lung > Breast >> Melanoma | Found at the gray/white matter junction. |
Activity:
3. Bone Metastasis Types
Metastatic disease in the bone can alter bone density in different ways depending on the tumor type.
| Type | Description | Examples |
|---|---|---|
| Blastic (Sclerotic) | Increased bone density / New bone formation. | Prostate, Small cell lung cancer. |
| Lytic | Bone destruction / “Punched-out” lesions. | Kidney, Colon, Non-small cell lung cancer. |
| Mixed | A combination of both. | Breast cancer. |
Activity
High-Yield Mnemonics & Tips:
- The “Hematogenous” Four: Remember that most carcinomas go through lymph, but Four Carcinomas Route Hematogenously (FCRH): Follicular thyroid, Choriocarcinoma, Renal cell, and Hepatocellular.
- Prostate & Bone: Prostate cancer is the classic example of blastic (sclerotic) bone lesions. Look for an older man with back pain and high PSA.
- Brain Junction: Brain metastases classically settle at the gray/white matter junction because that is where the blood vessels narrow and trap tumor emboli.