sentinel lymph node biopsy
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sentinel lymph node biopsyA procedure, performed most often for breast cancer and less commonly for melanomas, in which a dye (Patent Blue V) and/or radioactive substance (99mTc-labelled colloid) is injected near a tumour; it flows into the sentinel lymph node (the first lymph node that cancer spreads to from a primary cancer). In the breast, 90% of the sentinel nodes are in the axilla, 10% in the internal mammary chain. The sentinel lymph is identified by a dye or a handheld gamma probe, removed and sent to pathology. If the sentinel node is negative for cancer (about 5% of cases are false negative), then it is likely that the tumour has not spread to the nodes and the considerable morbidity associated with removing the lymph nodes (e.g., marked lymphoedema with compromised quality of life, restricted shoulder movement, sensory loss, seroma formation, longer hospital stay and future risk of angiosarcoma) can be avoided.
Macrometastasis: 50% risk of non-sentinel lymph node involvement.
Micrometastasis: Breast, 20% risk of non-sentinel lymph node involvement.
Predictors of poor prognosis
• Presence of infiltration of the sentinel node capsule;
• Tumour penetrative depth of > 2 mm;
• Largest tumour deposit of 30 cells.
Metastasis detected by immunocytochemistry, 9% risk of non-sentinel lymph node involvement.