Sentinel Lymph Node Biopsy and Axillary Dissection

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CHAPTER 23 Sentinel Lymph Node Biopsy and Axillary Dissection

Robert E. Roses

Case Study

A 55-year-old male presents for evaluation of a pigmented lesion on his upper mid-back. He notes that the lesion has increased in diameter, has become raised, and has changed coloration over the past several months. He is fair skinned, with blue eyes and blond hair. He reports a history of blistering sunburns as a teenager. An asymmetric lesion with a maximal diameter of 1 cm and variegated brown coloration is noted on his mid-back. He has multiple other pigmented lesions scattered over his trunk and extremities. No adenopathy in his axillae, neck, or groin is appreciated. A punch biopsy shows a malignant melanoma with a thickness of 2.9 mm.

BACKGROUND

Lymph node staging is an important component of the surgical management of both malignant melanoma and breast cancer. Until the 1990s, complete regional lymphadenectomy represented the standard approach to achieving this goal. The development of sentinel lymph node biopsy has allowed for the more limited, selective treatment of regional lymph nodes and has decreased the number of complete regional dissections performed in patients without nodal metastases. This procedure, as it is currently performed, maps the lymphatic drainage from the skin or breast to a primary lymph node or nodes, using a vital blue dye or a radioisotope-labeled tracer. Surgical excision and pathologic evaluation of these nodes for metastases allows for reliable staging and the prediction of additional lymph node metastases. Generally, patients found to have metastases in the sentinel node or nodes (i.e., positive sentinel node biopsy) undergo completion lymphadenectomy. In contrast, patients with negative findings on sentinel lymph node biopsy can safely forgo lymphadenectomy in view of the very low risk of nonsentinel nodal involvement. Sentinel lymph node biopsy also allows a meticulous histologic evaluation of multiple sections augmented by immunohistochemical staining for melanoma-related antigens and cytokeratins for breast cancer. This, not infrequently, allows more precise staging of both diseases.

With few exceptions, the axillary lymph nodes represent the first site of metastasis from melanomas of the upper extremities and upper trunk and cancers of the breast. This chapter focuses on axillary lymph node biopsy; however, the techniques described are applicable to sentinel lymph node biopsy performed at other sites (e.g., the groin for lower extremity melanomas and the cervical, parotid, and occipital lymph nodes for head and neck melanomas). Axillary dissection, which remains an important component of the management of breast cancer and melanoma and typically follows a positive finding on sentinel lymph node biopsy, is also described.

INDICATIONS FOR SURGERY

I. Breast Cancer

A. Patients with invasive breast cancer who can safely undergo surgery benefit from lymph node staging. This is generally achieved through sentinel lymph node biopsy. Exceptions include patients with axillary lymphadenopathy suspicious for metastatic disease and patients who have had previous breast or chest wall irradiation, which may disrupt the lymphatics and preclude accurate lymphatic mapping. Such patients should forgo sentinel lymph node biopsy in favor of axillary dissection. Elderly patients or those with significant comorbidities, with favorable stage I tumors, also may forgo sentinel lymph node biopsy.
B. Although patients with in situ breast cancers should not, theoretically, have nodal metastases, invasive foci in the area of the in situ disease is present in 10% to 30% of patients. A number of indications for sentinel lymph node biopsy in patients with ductal carcinoma of the breast (DCIS) have, therefore, emerged. Sentinel lymph node biopsy is indicated in patients with multicentric or broad areas of high-grade DCIS, as well as in those undergoing total mastectomy (which precludes subsequent nodal staging without axillary dissection).

II. Melanoma is the eighth most common cancer in the United Stated and the most common cause of skin cancer–related deaths. Tumor thickness is the dominant prognostic factor and is correlated with the risk of regional metastasis. Generally, sentinel lymph node biopsy is offered to patients with melanomas exceeding 1 mm in thickness. Completion lymphadenopathy is performed if the sentinel node is found to contain metastatic disease. Patients with “intermediate-thickness” melanomas (1–4 mm) are at relatively higher risk of having nodal metastases compared with patients with thinner lesions, but they are at lower risk, compared with patients with thicker lesions, of having distant metastases. Notably, the therapeutic utility of sentinel lymph node biopsy in patients with such lesions was recently evaluated in the Multicenter Selective Lymphadenectomy Trial. This trial compared wide local excision and sentinel lymph node biopsy with wide local excision alone for the treatment of intermediate-thickness melanomas and demonstrated a survival advantage for patients randomized to the former treatment group who had nodal micrometastases.

PREOPERATIVE EVALUATION

The components of the preoperative evaluation of patients with breast cancer and melanoma are distinct and are discussed separately.

I. Breast Cancer

A. The evaluation of a suspected breast cancer typically includes breast examination, mammography, and breast biopsy. Additional diagnostic modalities increasingly used in the evaluation of breast lesions include ultrasound and magnetic resonance imaging. The goals of this evaluation are to: (1) establish a tissue diagnosis, (2) clinically stage patients, and (3) identify candidates for breast-conserving therapy versus patients who require mastectomy.
B. An assessment for regional metastases should begin with a physical examination of the bilateral axillary and supraclavicular fossae. Adenopathy suggestive of metastatic disease may be further evaluated with fine-needle aspiration; malignant cells seen on cytologic evaluation or a high degree of suspicion for nodal metastases should prompt axillary dissection rather than sentinel lymph node biopsy.

II. Melanoma

A. The evaluation of a suspected melanoma begins with a biopsy to both diagnose and microstage the lesion if proven to be a melanoma. Excisional biopsy (i.e., removal of the lesion with grossly negative margins) is the optimal technique for smaller lesions. A punch biopsy directed at the clinically thickest area is sufficient for larger lesions. Shave biopsies may preclude accurate assessment of tumor thickness and should be avoided. After biopsy, tumor thickness is characterized on the basis of anatomic level of invasion (Clark level) and, most importantly, by thickness in millimeters (Breslow thickness

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