Sentinel Lymph Node Biopsy for Squamous Cell Carcinoma

Updated: Sep 26, 2016
  • Author: Keith M Baldwin, DO; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Overview

Background

Cutaneous squamous cell carcinoma (SCC) is a malignant tumor of keratinizing epidermal cells. This type of skin cancer is the second leading cause of skin cancer death after melanoma, and it is the second most common type of nonmelanoma skin cancer after basal cell carcinoma.

Most SCCs occur on the sun-exposed areas of the head and the neck. The most common route of spread for metastatic SCC is lymphatic in nature. In SCC of the upper aerodigestive tract, especially the neck, both the investigation and the treatment of a patient with a clinically N0 neck remain controversial. Depending on the classification of the tumor according to the TNM staging system, approximately 30% of patients with SCC of the head and neck have subclinical metastases in the neck, and knowledge of lymph node disease alters management. [1, 2, 3]

Although CT scanning and MRI are commonly used to classify tumors of the neck, their overall accuracy is limited. The only highly accurate means of identifying lymph node disease is to perform a staging lymph node dissection. For disease in its early stages, clinicians are reluctant to perform an elective lymph node dissection because of the associated morbidity and lack of beneficial effects.

For more information, see Head and Neck Squamous Cell Carcinoma.

The sentinel lymph node

The sentinel lymph node (SLN) is the first lymph node to drain a metastatic tumor cell that drains via the lymphatic route. The concept of the SLN is based on the orderly progression of tumor cells within the lymphatic system. Mapping of the lymph flow from the tumor site to the regional lymphatic drainage area can be used to identify the primary draining lymph node (ie, SLN). If the SLN can be identified and examined for the presence of tumor metastases, an elective lymph node dissection for staging may not need to be performed.

The concept of the SLN originated in 1977 when Cabanas described mapping of the first lymph node–draining penile carcinoma. In 1977, Robinson et al described the use of cutaneous lymphoscintigraphy in the nodal basin for truncal melanomas using colloidal gold scanning. The development of lymphatic mapping at the end of the 1980s was a breakthrough in making the sentinel node concept applicable to various types of malignancies, particularly breast cancer and melanoma.

In 1993, Alex et al introduced the use of technetium-99m sulfur colloid, a radioactive tracer, which is injected intradermally around a primary melanoma site, followed by an imaging study and subsequent intraoperative use of a gamma probe to localize the sentinel node. [4] Initial results of the SLN procedure in carcinoma of the head and the neck have been reported with mixed success. In a series of cases using radiocolloid alone, Koch et al remained unconvinced of its role in the management of patients with carcinoma of the head and neck. [5] Pitman et al were unable to find any lymph nodes that stained blue in patients who were injected with blue dye alone. [6] Alex and Krag performed the first successful SLN biopsy of the head and neck on a patient with a supraglottic carcinoma. [7]

Incidence and prevalence of SCC

Approximately 100,000 cases of SCC are diagnosed in the United States each year. Approximately 80% of ultraviolet light–induced SCCs develop on the arms, head, or neck. The frequency of cutaneous SCC, as with all nonmelanoma skin cancers, is increasing.

Etiology

Any of the following may cause SCC:

  • Exposure to sunlight
  • Chemical carcinogens, such as arsenic and hydrocarbons
  • Human papillomavirus
  • Ionizing radiation
  • Cigarette smoke
  • Chronic irritation or ulceration
  • Alcohol

In addition, immunocompromised patients have a much higher risk of developing SCC. Two genes, PATCHED and TP53, have been identified that usually prevent cancers but are inactivated in patients with SCC; TP53 is mutated in more than 90% of patients with SCC.

Clinical manifestations

SCC arises from basal keratinocytes of the skin. It typically manifests as a firm nodule on an erythematous base with elevated borders and insidious margins. Central ulceration or crusting may be present. Irregular nests of epidermal cells invading the dermis in varying degrees characterize SCC. Grading is based on the degree of cell differentiation. The most common route of spread for metastatic SCC is lymphatic in nature.

SCCs of the skin typically manifest on the head, neck, or arms. They usually have elevated and rolled edges with central ulceration. Well-differentiated SCCs are likely to manifest as firm erythematous nodules of varying sizes, sometimes with an area of central hyperkeratosis. The tumor is usually firm, although tumors in more advanced cases can be soft and friable. Erosion and ulceration are more common with SCCs. Poorly differentiated SCCs are more apt to manifest as faintly erythematous nodules or plaques that are not well defined; ulceration is also common.

See the image below.

Large, sun-induced squamous cell carcinoma (SCC) o Large, sun-induced squamous cell carcinoma (SCC) on the forehead/temple. Image courtesy of Glenn Goldman, MD.

Successful SLN biopsy

Defining a successful SLN biopsy accurately is critical. Although some studies have examined the impact of an individual surgeon's experience on the SLN identification rate, SLN identification is clearly not an appropriate endpoint; many studies have documented excellent SLN identification rates with unacceptably high false-negative rates. The more important issue is the experience required to achieve an acceptably low false-negative rate. In cases in which the pathology results from the scintigram are unclear or are negative, a formal elective neck dissection should be considered for staging purposes.

This procedure is multidisciplinary. As such, surgeons must ensure that nuclear medicine specialists, radiologists, and pathologists are actively involved with the successful implementation of this new technology. The learning curve for individual surgeons is undoubtedly associated with the experience levels of specialists within the multidisciplinary team. The implications of the SLN procedure must be effectively communicated to radiation oncologists and medical oncologists. The coordination of effort among the various specialists in each discipline is an essential component of the learning process.

The role of the SLN biopsy in the management of SCC of the head and the neck will evolve as more centers accept it as a potential standard of care. [8, 9, 10]

Patient education

For patient education information, see the Cancer and Tumors Center, as well as Skin Cancer, Skin Biopsy, and Cancer of the Mouth and Throat.

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Indications

Elective dissection of a clinically negative (ie, N0) neck causes overtreatment for many early stage (T1, T2) patients, while no equivocal advantage in survival has been demonstrated when compared with a delayed dissection for patients with metastases in the neck in this group. SLN biopsy can help determine the presence of lymph node metastases in patients with T1-T2, N0 oral and oropharyngeal SCCs.

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Contraindications

Contraindications to SLN biopsy are a palpable lymph node, tumors larger than 4-5 cm, disruption of lymphatic drainage, prior extensive surgery (eg, dissection of the neck), previous radiation to the head and the neck, and allergy to dye.

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Outcomes

The sentinel lymph node (SLN) biopsy can be a valuable staging technique for patients with squamous cell carcinoma whose lymphatic drainage of the neck has not been altered by previous surgery or radiotherapy. It provides reliable detection of micrometastasis, indicating which levels should be removed ipsilaterally or contralaterally. This technique also allows the surgeon to accurately plan a dissection of the neck, taking into consideration the pattern of lymphatic drainage of each patient. In this way, unnecessary dissection of the neck and its morphofunctional sequelae can be avoided in numerous patients.

The cumulative results of all those who contributed to the first international conference on SLN biopsy of mucosal cancer of the head and the neck confirm that SLN biopsy has a role in staging the clinically N0 neck, and it has a similar sensitivity to that of a neck dissection for staging.

Complications of SLN biopsy

Allergic reactions to isosulfan blue, nerve injury, lymphedema, neuropathy, fat necrosis, seroma, and hematoma can result following dissection of an SLN.

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