How can Tc-99m be used for sentinel lymph node mapping?

• A. It highlights healthy lymph nodes
• B. It identifies the first lymph node(s) likely to be affected by cancer
• C. It monitors overall lymphatic drainage
• D. It provides therapeutic radiation to lymph nodes

Answer: (B)

Tc-99m is a radiopharmaceutical that plays a crucial role in the process of sentinel lymph node mapping, particularly in oncology. The correct choice indicates that Tc-99m is used to identify the first lymph node or nodes that are likely to be affected by cancer, known as the sentinel lymph nodes.

When a cancerous tumor is present, lymphatic drainage will typically first occur to these sentinel nodes. By injecting Tc-99m-labeled colloid near the tumor site, the radiopharmaceutical travels through the lymphatic system to the sentinel lymph nodes. This allows for imaging techniques, such as gamma scintigraphy, to locate these nodes. Monitoring these specific nodes is vital because if cancer cells are detected in them, it may indicate that the cancer has begun to spread, whereas negative findings can suggest that the cancer has not metastasized, impacting treatment decisions.

This targeted mapping allows clinicians to better assess the extent of cancer spread and to decide on appropriate surgical interventions, such as sentinel lymph node biopsy, which can help avoid unnecessary removal of additional lymph nodes, thus sparing patients from potential complications and side effects.