In melanoma, a sentinel lymph node biopsy is performed, as in breast cancer, only if all other diagnostic methods have not shown the presence of distant metastases. If there are already metastases in distant organs and lymph nodes, a biopsy will be useless, it will not change anything for the patient. However, if standard studies have not shown the presence of metastases, we cannot be sure that there are no micrometastases left in the lymph nodes, and therefore we perform a biopsy of the sentinel lymph node.
Most often, by the time of this study, the tumor itself has already been removed, and its histological characteristics are known. Diagnostic decisions are made depending on these characteristics. If the germination depth is large, it is advisable to do PET-CT scan to make sure that there are no distant metastases. If there are none, a sentinel lymph node biopsy is performed. If the germination is less than 2 mm (according to Breslow), a sentinel lymph node biopsy is performed immediately.
The radiopharmaceutical, which is an isotope-labeled colloid, is injected intradermally, around the melanoma, if it has not yet been removed, or around the scar that remains after its excision at a distance of 1.5-2 cm. There are usually 4 injection points, but if the scar is long, then there may be 6. After 15-20 minutes, when the lymph is already beginning to drain actively enough, visualization is performed. Most often – with the help of a gamma camera. If the location of the lymph node is unclear (which is often the case with trunk melanoma, when lymph outflow is unpredictable), an additional SPECT-CT scan is performed. This is a hybrid imaging method that allows you not only to see the sentinel lymph node, but also to link it to the anatomy and clearly show surgeons where it is located.
After that, a marking is performed on the skin, and during the operation (on the same day or the next), the surgeon uses a gamma probe, as in the case of breast cancer, to bring the lymph nodes to a small incision in the skin and check. If they are active, they are removed, if inactive, they are left in place.
Usually, from 1 to 4 lymph nodes are removed, and they are sent for histological examination. If all of them are clean, the probability that the melanoma has metastasized is less than 2%.
What happens if you do not perform a sentinel lymph node biopsy for melanoma?
The first option is an extended lymph dissection for excision of melanoma. This is a crippling operation, which has huge volumes, traumatizes and invalidates the patient. Given that the lymph outflow from melanoma is unpredictable in some locations, this operation may not be performed in the area where the lymph is actually flowing and is useless.
If an extended lymph node dissection is not performed, there is a possibility that micrometastases remain, which can lead to a recurrence.
Sentinel lymph node biopsy is a widely used worldwide standard technique for the diagnosis of micrometastases in melanoma and breast cancer, but it can also be used in other diseases such as prostate cancer, cervical cancer, cancer of the mouth, nose, nasopharynx. Multiple studies are underway in this area, but such techniques are not yet standard and can only be recommended to patients according to individual indications by their attending physicians href="/directions/klinika-dermatovenerologii-i-allergologii-immunologii_dermatoonkologiya/doctors/">дерматологами-онкологами.
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