Determination of Melanoma Lateral and Depth Margins: Potential for Treatment Planning and Five-Year Survival Rate

Abstract

Cutaneous malignant melanoma (CMM) is a serious type of cancer accounting for 75% of all deaths associated with skin cancer (Jerant et al., 2000). CMM incidence has dramatically increased in the past few decades and, recently, approximately 160,000 new cases of CMMs are diagnosed worldwide each year (Ries et al., 2003). In 2010, the American Cancer Society estimated that 68,130 cases of melanoma (38,870 males; 29,260 females) and 8,700 melanoma deaths (5,670 males; 3,030 females) were expected in the United States (American Cancer Society (ACS), 2010). In the United States, the lifetime risk for developing CMM has increased from 1 in 1500 in 1930 to 1 in 50 in 2010 (ACS, 2010; King, 2004). Proper staging of CMM is crucial for defining prognosis and for determining the optimal treatment approach. Several cancer staging systems are being used worldwide. One of the most common staging systems is the tumor-node-metastasis (TNM) classification established by the American Joint Committee on Cancer (AJCC) (Balch et al., 2001). The TNM system classifies CMM in three categories: (1) the size and extent of the primary tumor (T), (2) the involvement of regional lymph nodes (N) and, (3) the presence or absence of distant metastasis (M), determining CMM clinical Stage I, II, III, or IV. To remain current and relevant to clinical practice, the TNM classification is updated periodically based on advances in understanding of cancer prognosis. The latest revision of TNM (presented in the 7th edition of the AJCC Cancer Staging Manual) is applied for cases diagnosed on or after January 1, 2010 (Edge et al., 2010). The CMM invasion depth known as the Breslow thickness (Breslow, 1970) in T category is the single most important factor for CMM staging and closely related to survival rate (Mihm et al., 1988). The five-year survival rate is 95%100% if CMM thickness is less than 1 mm, while the survival rate is reduced to 50% if the tumor thickness is greater than 4 mm (Figure 1). Current surgical treatment for primary CMM has often been an excision with a margin determined by CMM thickness (Table 1). Since the risk of local recurrence is dependent on CMM thickness, a narrow margin of 5 mm is recommended for in situ CMMs, 1 cm for tumors thinner than 1 mm, 1-2 cm for tumors between 1.01 and 2 mm, and 2 cm for tumors thicker than 2.01 mm (Sladden et al., 2009). Because sentinel lymph node highly correlates with the metastatic status of CMM, a sentinel lymph node dissection (SLND) procedure is also performed on patients with intermediate thickness (1-4 mm) lesions (Balch & Ross,