General Information About Melanoma
Incidence and Mortality
Estimated new cases and deaths from melanoma in the United States in 2014:
- New cases: 76,100.
- Deaths: 9,710.
The incidence of melanoma has been increasing over the past four decades. Risk factors for melanoma include the following:
- Sun exposure.
- Pigmentary characteristics.
- Multiple nevi.
- Family and personal prior history of melanoma.
- Environmental exposures.
(Refer to the PDQ summary on Genetics of Skin Cancer for more information about risk factors.)Histopathology
Melanoma is a malignant tumor of melanocytes, which are the cells that make the pigment melanin and are derived from the neural crest. Although most melanomas arise in the skin, they may also arise from mucosal surfaces or at other sites to which neural crest cells migrate. Melanoma occurs predominantly in adults, and more than 50% of the cases arise in apparently normal areas of the skin. Early signs in a nevus that would suggest malignant change include darker or variable discoloration, itching, an increase in size, or the development of satellites. Ulceration or bleeding are later signs. Melanoma in women occurs more commonly on the extremities and in men, it occurs most commonly on the trunk or head and neck, but it can arise from any site on the skin surface. A biopsy, preferably by local excision, should be performed for any suspicious lesions, and the specimens should be examined by an experienced pathologist to allow for microstaging. Suspicious lesions should never be shaved off or cauterized. Studies show that distinguishing between benign pigmented lesions and early melanomas can be difficult, and even experienced dermatopathologists can have differing opinions. To reduce the possibility of misdiagnosis for an individual patient, a second review by an independent qualified pathologist should be considered.Prognostic Factors
Prognosis is affected by clinical and histological factors and by anatomic location of the lesion. Thickness and/or level of invasion of the melanoma, mitotic index, presence of tumor infiltrating lymphocytes, number of regional lymph nodes involved, and ulceration or bleeding at the primary site affect the prognosis.[3-6] Microscopic satellites in stage I melanoma may be a poor prognostic histologic factor, but this is controversial. Patients who are younger, female, and who have melanomas on the extremities generally have a better prognosis.[3-6]Follow-up and Survival
Clinical staging is based on whether the tumor has spread to regional lymph nodes or distant sites. For disease clinically confined to the primary site, the greater the thickness and depth of local invasion of the melanoma are, the higher the chance of lymph node or systemic metastases, and the worse the prognosis is. Melanoma can spread by local extension (through lymphatics) and/or by hematogenous routes to distant sites. Any organ may be involved by metastases, but lungs and liver are common sites. The risk of relapse decreases substantially over time, though late relapses are not uncommon.[8,9]Related Summaries
Other PDQ summaries containing information related to melanoma include the following:References
- American Cancer Society.: Cancer Facts and Figures 2014. Atlanta, Ga: American Cancer Society, 2014. Available online. Last accessed February 14, 2014.
- Corona R, Mele A, Amini M, et al.: Interobserver variability on the histopathologic diagnosis of cutaneous melanoma and other pigmented skin lesions. J Clin Oncol 14 (4): 1218-23, 1996. [PUBMED Abstract]
- Balch CM, Soong S, Ross MI, et al.: Long-term results of a multi-institutional randomized trial comparing prognostic factors and surgical results for intermediate thickness melanomas (1.0 to 4.0 mm). Intergroup Melanoma Surgical Trial. Ann Surg Oncol 7 (2): 87-97, 2000. [PUBMED Abstract]
- Manola J, Atkins M, Ibrahim J, et al.: Prognostic factors in metastatic melanoma: a pooled analysis of Eastern Cooperative Oncology Group trials. J Clin Oncol 18 (22): 3782-93, 2000. [PUBMED Abstract]
- Balch CM, Buzaid AC, Soong SJ, et al.: Final version of the American Joint Committee on Cancer staging system for cutaneous melanoma. J Clin Oncol 19 (16): 3635-48, 2001. [PUBMED Abstract]
- Slingluff CI Jr, Flaherty K, Rosenberg SA, et al.: Cutaneous melanoma. In: DeVita VT Jr, Lawrence TS, Rosenberg SA: Cancer: Principles and Practice of Oncology. 9th ed. Philadelphia, Pa: Lippincott Williams & Wilkins, 2011, pp 1643-91.
- León P, Daly JM, Synnestvedt M, et al.: The prognostic implications of microscopic satellites in patients with clinical stage I melanoma. Arch Surg 126 (12): 1461-8, 1991. [PUBMED Abstract]
- Shen P, Guenther JM, Wanek LA, et al.: Can elective lymph node dissection decrease the frequency and mortality rate of late melanoma recurrences? Ann Surg Oncol 7 (2): 114-9, 2000. [PUBMED Abstract]
- Tsao H, Cosimi AB, Sober AJ: Ultra-late recurrence (15 years or longer) of cutaneous melanoma. Cancer 79 (12): 2361-70, 1997. [PUBMED Abstract]