Breast Cancer staging and diagnosis using sentinel lymph-node biopsy

A sentinel lymph node biopsy is a relatively new procedure that was developed to identify metastasis of breast cancer to the axillary lymph nodes, but without having to do a traditional axillary lymph node dissection. The lymph ducts of the breast usually drain to one lymph node first, before draining through the rest of the lymph nodes underneath the arm. This initial lymph node is called the sentinel lymph node, and a sentinel lymph node biopsy removes this lymph node only. The sentinel lymph node may be identified either by a weak radioactive dye (technetium-labeled sulfur colloid) or by a blue dye (isosulfan blue) that stains the lymph tissue a bright blue color.

In addition to practical advantages such as removing the need for an overnight hospital stay and various recuperative physical therapy exercises, the sentinal lymph node biopsy typically leads to a more accurate assessment of whether the cancer has spread to the lymph nodes. A negative sentinel lymph node presents a very very high probability that the remaining axillar lymph nodes are also cancer free.

The sentinal node biopsy is indicated when a percautaneous needle biopsy shows an infiltrating lesion, but a clinical exam of the axilla is negative. When the sentinel node is negative for cancer, no surgical intervention is necessary, but if it is positive, then 8-12 axillary lymph nodes are typically dissected for further biopsy.

Sentinel lymph node biopsies are usually taken when the TNM classification is T1-2 N0 (tumor size 2-5 cm ), but not for T3. At TNM T3, the size of the tumor is greater than 5 cm and there is a very high probability of lymphatic involvement.

Failure to identify the sentinel node may indicate that it has been compromised, and should be followed by a full axillary node dissection and biopsy. However, sentinel node biopsy is contraindicated for women with multiple tumors, previous breast surgery, or previous radiation therapy, or for women who have obviously palpable nodes.

The histopathological report on SLNs usually includes the total number of sentinel lymph nodes received, any macroscopic involvement, the number of lymph nodes affected by metastatisis, and the what extent. SLN reports often also state whether there is nodal involvement detected through special techniques such as immunostaining and molecular analysis. At a mimimum, the SLN report should identify all macrometastases greater than 2 mm.

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