Satellite metastasis

A satellite metastasis is a small group of cancer cells that has spread just beyond the main tumour but remains very close to it. These small tumours are usually found within 2 centimeters of the primary tumour and have not yet traveled to lymph nodes or distant organs. Satellite metastases are most commonly seen in melanoma, but they can also occur in other types of cancer.

Why is a satellite metastasis important?

The presence of a satellite metastasis means that the cancer is spreading locally and may be more aggressive. It can also indicate a higher chance that the cancer could spread further, including to lymph nodes or other parts of the body. Because of this, finding a satellite metastasis may change the tumour stage and influence treatment decisions.

How is this diagnosis made?

Satellite metastases are usually found during a physical exam, imaging tests, or a biopsy. A doctor may notice small nodules or spots near the original tumour, often in the skin for melanoma cases. Ultrasound, CT scans, or MRI may be used to confirm the presence of these small metastases. If needed, a biopsy is performed to confirm that the cells in the satellite metastasis match those of the primary tumour.

What is the difference between a satellite metastasis and an in transit metastasis?

The key difference between satellite metastases and in transit metastases is their location. Satellite metastases are small tumours located very close (within 2 cm) to the primary tumour. In contrast, in transit metastases are found farther away, between the primary tumour and the nearest lymph nodes. Both types of metastases indicate that the cancer is spreading, but in transit metastases suggest a more advanced stage.

How does a satellite metastasis affect the tumour stage?

The presence of satellite metastases can increase the stage of the cancer because it means that cancer cells have already spread beyond the main tumour. In melanoma, for example, the presence of satellite metastases usually classifies the cancer as stage III, which is more advanced than earlier stages but may still be treatable with surgery, immunotherapy, or other treatments. The exact impact on staging depends on the type of cancer and the extent of spread.