What is a Sentinel Lymph Node Biopsy?
Cancer develops in a primary organ, e.g. the breast, and spreads via lymphatics and blood stream in a stepwise fashion. The draining lymph nodes are first in the line of spread and staging of the cancer involves checking the lymph nodes for actual evidence of spread. This is achieved by surgically removing a large sampling of lymph nodes, via a surgical procedure called Lymph Node Dissection. This often disrupts normal lymphatic channels, which causes drainage problems for normal lymph drainage. This results in swelling upstream, called lymphedema.
A Sentinel Lymph Node Biopsy targets the Sentinel Lymph Node, which is the first to drain downstream from the tumor site. This is identified by injecting a blue dye, as well as a radioactive dye into the tumor site, seeing where it drains and only resecting the targeted lymph node. If this lymph node is involved with cancer cells, the dissection is carried to completion. If not, the lymph nodes are deemed not to be involved. This spares the patient the unnecessary consequences of lymphedema.
This procedure is currently useful in only 2 types of cancers, where spread occurs in a stepwise fashion: melanoma and breast cancer. Other internal cancers, e.g. lung or colon do not benefit, because the primary surgery requires segmental removal of the involved organ, and the attached lymph nodes.