Sentinel Lymph Node Biopsy
A Publication of OakLeaf Medical Network, Inc, March 2000.
This year, sentinel node biopsy has been added as a new procedure performed at the Oak Leaf Surgery Center. This procedure is done for melanoma and breast cancer, and to this date has not been performed elsewhere in the Chippewa Valley.
In order to develop a protocol for this procedure, there has been extensive cooperation between surgery, radiology and pathology. The Surgery Center purchased a state-of-the-art US Surgical gamma probe to facilitate locating the sentinel nodes. CMI has arranged to bring in mobile scanning equipment as well.
What is a sentinel node?
Breast cancer or melanoma may spread to the regional lymph nodes. It has been recently demonstrated that a tumor will spread to the sentinel node first before it spreads to the other nodes in the regional chain. Clinical studies have shown that if the sentinel node is free of cancer the other lymph nodes will most probably be free of cancer. The goal of this procedure is to determine which patients do not have lymph node metastases and spare them a complete lymph node dissection.
By injecting Technesium 99m sulfur colloid around the tumor and allowing it to migrate to the regional nodes, we can see which lymph node chains concentrate the radionucleotide. This is particularly useful for melanomas of the trunk since we cannot predict which axilla or groin may be involved. Once the particular chain is demonstrated, individual nodes can be identified as the sentinel nodes by their degree of radioactivity.
There may be between one and five sentinel nodes. The pathologist performs a more detailed examination of sentinel nodes than the usual node analysis. At present we are performing complete node dissections on our patients to confirm that our node mapping technique is accurate. So far, our two initial patients have had both negative sentinel nodes and negative complete dissections; giving us 100% correlation. Once we have had a large enough series of patients, and have demonstrated good correlation, we will be able to avoid the complete dissections in sentinel node negative patients.
How is the sentinel node mapping done?
This is done in situations where we already know that a patient has a breast cancer or melanoma because the patient has had either a needle biopsy or a surgical biopsy. Before the sentinel node biopsy is done, the patient has the area around the tumor (or biopsy site) injected with radionucleotide. This is done at the Surgery Center. For breast lesions, this is done the afternoon before the biopsy, for melanomas only about an hour pre-op.
After the injection, a lymphoscintogram is done with a gamma camera to see which lymph glands have concentrated the radionucleotide. This gives us a general idea which lymph glands we have to be prepared to biopsy. There are times that the sentinel nodes are not in an expected area at all, such as a breast tumor that localizes to the internal mammary chain.
Developing a protocol for this procedure and obtaining the proper equipment was a complex process. However, it has been successful because of the HealthSouth OakLeaf Surgery Centerís commitment to providing state-of-the-art, quality care to the patients of the Chippewa Valley.