(1)
Department of Surgery Division of Surgical Oncology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
Introduction
The differential diagnosis of peripheral lymphadenopathy is long and includes disorders that range from the inconsequential to the rapidly fatal. As a result, surgeons are often called upon to biopsy a lymph node in order to provide the tissue needed to establish the diagnosis (Figs. 22.1 and 22.2).
Fig. 22.1
CT scan image of a patient with diffuse cervical lymphadenopathy associated with a non-Hodgkin’s lymphoma
Fig. 22.2
CT scan image of a patient with bilateral axillary lymphadenopathy of unknown etiology for excisional lymph node biopsy
Lymph nodes can become enlarged for benign reasons such as inflammation, immunosuppression, or in response to a viral or bacterial infection. Features of benign lymph nodes are that they tend to be mobile, tender, have a rubbery consistency, and that—even though enlarged—they retain their elliptical shape. Location is also a useful indicator; for example, the neck is an extremely common site of benign lymphadenopathy, whereas an enlarged supraclavicular node is highly suspicious for malignancy. If a node is of low concern, it may be simply observed for a brief period of time. If the lymphadenopathy regresses, no further evaluation is needed. However, persistent or diffuse lymphadenopathy should be evaluated by biopsy.
Lymph nodes may become involved by a primary malignancy such as lymphoma, or may be infiltrated by metastases from another site. Certain malignancies, such as breast cancer, tend to have an orderly progression through the local lymph nodes before metastasizing to distant organs. However, it is important to realize that other cancers such as most sarcomas, are not associated with nodal involvement, even in advanced stages.
A sentinel lymph node refers to the first node that drains a given part of the body. In the setting of cancer, the sentinel lymph node represents the first stop for tumor cells that are in the process of metastasizing from the primary tumor. Biopsy of the sentinel node allows physicians to determine whether or not a tumor has begun to metastasize (Fig. 22.3). If there are no tumor cells in the sentinel node, it is unlikely that tumor is present in any of the downstream nodes. While not every tumor type metastasizes in this orderly manner, sentinel lymph node biopsy has proven especially reliable in breast cancer and melanoma. If the sentinel node is positive for tumor, a completion lymphadenectomy may be indicated, but by performing a sentinel biopsy first, most patients can be spared a full nodal dissection and its accompanying risks.
Fig. 22.3
Injection of blue dye into a melanoma lesion in order to identify the sentinel lymph node [Reprinted from Winqvist O, Thörn M. Sentinel Node. In: Schwab M (ed). Encyclopedia of Cancer. Heidelberg, Germany: Springer Verlag; 2009: 2702-2705. With permission from Springer Verlag]
Surgical Technique
In patients with lymphadenopathy of unknown etiology, an excisional lymph node biopsy can be performed for tissue analysis. A small incision is made over the site of lymphadenopathy and the adipose tissue is dissected away to the level of the node. The target lymph node is placed on traction and its surrounding attachments are divided. The lymphovascular pedicle should be isolated and formally ligated, particularly in large nodes, in order to prevent bleeding or a lymphatic leak.
A sentinel lymph node biopsy utilizes scintigraphy and/or blue dye, to localize the target node in a patient with known malignancy. In most cases, the site of lymphatic drainage is intuitive; breast cancers generally drain to the ipsilateral axilla. However, in cases such as a melanoma located on the trunk, the sentinel lymph node may be located in the axilla, groin, or a combination of sites. For sentinel lymph node biopsy, the primary tumor site is first injected in the nuclear medicine suite with a radiolabeled substance, typically sulfur colloid tagged with technetium-99. Images are then obtained which highlight the location and number of draining nodes.
These images are complemented by the use of vital blue dye; approximately 3 mL is injected around the tumor site once the patient is in the operating room. A small incision is made in the skin over the site identified by preoperative lymphoscintigraphy. The sentinel node is typically identifiable both by its blue stain and the presence of radioactivity as detected by a gamma probe. Although referred to as the “sentinel” node, it is not uncommon for multiple nodes to be identified. Generally, all nodes that stain blue, or that have >10 % of the radioisotope counts of the “hottest” node should be excised.
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