Sentinel Lymph Node Mapping-Pathology Protocol in Breast Cancer.

Sentinel Lymph Node Mapping-Pathology Protocol.

Sentinel lymph node mapping is now performed on selected patients who opt for conservative surgery to treat their breast cancer.
The procedure involves the surgical identification of those axillary lymph nodes that theoretically would be the first ‘‘sentinel’’ nodes to receive the lymphatic drainage from the breast harboring the invasive cancer. If these nodes are pathologically negative, the patient is spared the morbidity associated with a standard axillary node dissection.

Surgical identification is based on the peritumoral injection of radioactive solutions and/or colored dyes. The surgeon then massages the breast to facilitate permeation of the solution into the lymphatic system. Several hours after the injection, the patient is taken to the operating room, where the surgeon uses a radioactive counter to locate the ‘‘hot’’ lymph node. If a colored dye has been used, visual inspection of the axilla usually identifies the sentinel lymph node. Usually, the pathologist receives 1 to 3 lymph nodes for evaluation.

Some centers use cytologic imprints, either with or without frozen section evaluation,at the time of surgery to determine whether the sentinel node is involved by metastatic tumor. If the imprintsare positive, then the surgeon proceeds to an axillary node dissection. Other hospitals submit their sentinel lymph node biopsies for routine processing without intraoperative consultation.
Once the specimen is received in the pathology laboratory, the pathologist must carefully dissect out all the nodes and record the number and sizes. If it is technically feasible, each node should be serially sectioned at 2- to 3-mm intervals, parallel to the long axis, and entirely submitted for evaluation. One hematoxylineosin–stained section should be cut from each block for light microscopy. Additional unstained levels may also be requested at the time of sectioning, in the event that immunohistochemical analysis of the node will be required to confirm the diagnosis of metastatic disease. Although some studies advocate using immunohistochemistry on all histologically negative lymph nodes, the current College of American Pathologists guidelines state that this procedure is not the standard of care for pathologic evaluation of sentinel lymph nodes in patients with invasive breast cancer.

Metastasis and prognosisMacrometastases (>2 mm) have a clear influence on prognosis
Micrometastases (>0.2 mm, < or =" 2">
References:
Cserni G. Evaluation of sentinel lymph nodes in breast cancer. Histopathology 2005;46:697–702.
Weaver DL. Pathological evaluation of sentinel lymph nodes in breast cancer: a practical academic perspective from America. Histopathology 2005;46:702–6.
Bobrow L, Pinder S. Histopathology and the SLN. In: Sentinel lymph node biopsy handbook—NEW START. London: RoyalCollege of Surgeons of England; 2004. p. 88–94.