In the past several decades, the incidence of melanoma has steadily risen. In the United States, as of 2012, it is estimated that 76,250 new cases of melanoma will develop and 9,180 patients will die of the disease.1 Data from 2006 to 2008 projects that 1 in 36 males and 1 in 55 females will develop invasive melanoma during their lifetime.1 The median age of diagnosis is 59 years. Furthermore, the projected increase in the incidence of melanoma may be underestimated due to unreported outpatient treatments of superficial and in situ melanomas. Melanoma is one of the leading cancers in terms of average years of life lost per death from disease.2 Melanoma has higher incidence rates in lightly pigmented Caucasians than in Hispanics, Asians, and African Americans.2 Estimates indicate that 82% to 85% of patients present with localized disease, 10% to 13% with regional disease, and 2% to 5% with distant metastatic disease.3 Melanoma is responsible for the majority of skin cancer-related deaths but is often cured when detected early. Outcome depends on the stage at presentation.
Strong evidence supports three histologic features of the primary tumor to be of high prognostic value: tumor (Breslow) thickness, the presence or absence of microscopic ulceration, and mitotic rate. All three are required components of the biopsy specimen’s pathology report.4 Maximum Breslow thickness is measured from the granular layer of the epidermis or the base of a superficial ulceration to the deepest depth of invasion by malignant cells to the nearest 0.1 mm, excluding extension into the adnexal adventitia. Microscopic ulceration is defined as tumor-induced full-thickness epidermal loss with subjacent dermal tumor and reactive dermal changes. Mitotic rate is measured as the number of dermal mitoses per square millimeter.
In 2010 the American Joint Committee on Cancer (AJCC) defined an updated staging system in which tumor (Breslow) thickness and mitotic rate were identified as the two major factors that predict melanoma survival in tumors ≤1 mm in thickness.4 This change stemmed from the finding that a dermal mitotic rate ≥1 mitosis/mm2 is independently associated with a worse disease-specific survival. As a result, in the 2010 AJCC staging guidelines, the dermal mitotic rate was used to upstage patients with melanoma ≤1 mm from stage IA to stage IB, replacing the anatomic (Clark) level of invasion. The impact of tumor thickness on prognosis is underscored by variations reported in survival outcomes. In patients with localized disease and primary tumors ≤1.0 mm in thickness, over 90% of patients achieve 5 year survival. For patients with localized melanomas thicker than 1.0 mm, survival ranges from 50% to 90%.3 When the disease extends to regional nodes however, survival rates decrease by half.
BIOPSY OF A PRIMARY MELANOMA
The first step for definitive diagnosis of a cutaneous melanoma is to obtain a biopsy. A biopsy may be ...