Sentinel Lymph Node Biopsy

Roshni Dasgupta, MD MPH

Steps of the Procedure

What are the steps of sentinel lymph node biopsy?

Lymphoscintigraphy

  • The tracer is injected four to six hours prior to the operative procedure.
  • EMLA cream is placed on the primary or biopsy site one hour prior to the injection by patient or family in older patients who will have the procedure performed under local anesthesia. Younger patients will have the procedure performed under general anesthesia.
  • 0.1 ml aliquots of 125 µCi of Tc99m sulfur microcolloid are injected in four locations in the intradermal layers around the lesion or biopsy site.
  • Images are then obtained with a large field-of-view camera with a high resolution collimator until the optimal nodal uptake is visualized. The images should then be localized using lymphoscintigraphy and co-localized using cross sectional imaging. The surgeons should review with the radiologist the location of the nodes in order to guide the incision site.

lymphoscintigraphy
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Computerized tomographic lymphoscintigraphy allows better anatomic localization than planar images alone.

Intraoperative Technique

  • After adequate general anesthesia, 3 mL of lymphazurin 1% dye (isosulfan blue, Autosuture Norwalk Conn) is injected into the dermal layer in four quadrants surrounding the tumor or previous excision site.
  • The patient is then prepped and draped for the surgical procedure.
  • A gamma probe is then used to identify the area of maximal signal intensity in order to guide the dissection. An incision is then made overlying the area with the highest count on the gamma probe. Using a dual approach, sentinel lymph nodes are identified by uptake of radionuclide and blue dye.
  • After the first node is removed, it is moved away from the operative field and checked for a radioactive signal. The lymphatic basin should be rechecked and sentinel lymph nodes continue to be removed until the bed count is ten percent of the hottest lymph node (ex vivo count) consistent with background signal. All nodes should then be labeled appropriately and sent to pathology fresh for processing as sentinel lymph nodes.

sentinel lymph node
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Pathologic Evaluation

Direct communication with pathology is essential and a standardized protocol should be developed.

  • Serial sections and analysis by hematoxylin and eosin and subsequent immunohistochemical staining.
  • Nodes sectioned into five slides with two sent for immunohistochemistry (500 µm sections of entire nodes for rhabdomyosarcoma).

see also Breast Procedures

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Last updated: May 11, 2019