A melanoma is a tumor produced by the malignant transformation of melanocytes. Melanocytes are derived from the neural crest; consequently, melanomas, although they usually occur on the skin, can arise in other locations where neural crest cells migrate, such as the gastrointestinal tract and brain. The five-year relative survival rate for patients with stage 0 melanoma is 97%, compared with about 10% for those with stage IV disease.
The causes may be related to:
The incidence of malignant melanoma is rapidly increasing worldwide, and this increase is occurring at a faster rate than that of any other cancer except lung cancer in women. Melanoma is more common in Whites than in Blacks and Asians. Overall, melanoma is the fifth most common malignancy in men and the seventh most common malignancy in women, accounting for 5% and 4% of all new cancer cases, respectively. The average age at diagnosis is 57 years, and up to 75% of patients are younger than 70 years.Melanoma is notorious for affecting young and middle-aged people, unlike other solid tumors which mainly affect older adults. It is commonly found in patients younger than 55 years, and it accounts for the third highest number of lives lost across all cancers.
Melanomas may develop in or near a previously existing precursor lesion or in healthy-appearing skin. A malignant melanoma developing in healthy skin is said to arise de novo, without evidence of a precursor lesion. Solar irradiation induces many of these melanomas. Melanoma also may occur in unexposed areas of the skin, including the palms, soles, and perineum.
Certain lesions are considered to be precursor lesions of melanoma. These include the following nevi:
Melanomas have 2 growth phases, radial and vertical. During the radial growth phase, malignant cells grow in a radial fashion in the epidermis. With time, most melanomas progress to the vertical growth phase, in which the malignant cells invade the dermis and develop the ability to metastasize.
Clinically, lesions are classified according to their depth, as follows:
The 4 major types of melanoma, classified according to growth pattern, are as follows:
Most commonly, the history includes either changing characteristics in an existing mole or the identification of a new mole.
The characteristics of melanoma are commonly known by the acronym ABCDE and include the following:
Also, melanomas may itch, bleed, ulcerate, or develop satellites. Patients who present with metastatic disease or with primary sites other than the skin have signs and symptoms related to the affected organ system(s).
It is also important to examine all lymph node groups.
Perform excisional biopsy on suggestive lesions so that a pathologist can confirm the diagnosis. Shave biopsies and electrodesiccation are inadequate; a full thickness of skin is essential for proper histologic diagnosis and classification. The most important prognostic indicator for stage I and II tumors is thickness; obtain a full-thickness biopsy specimen for adequate pathologic interpretation. Biopsy results ultimately determine the margins of resection and which patients are candidates for sentinel lymph node biopsy and other adjuvant treatment.
The following laboratory studies are indicated:
The following imaging modalities may be considered:
Surgery such as wide local excision with sentinel lymph node biopsy, elective node dissection, or both is the definitive treatment for early-stage melanoma. When performing the wide local excision, first consider the surgical margins. If the primary closure is not feasible, skin grafting or tissue transfers may be needed. Medical management is reserved for adjuvant therapy of patients with advanced melanoma.
Agents that may be used in adjuvant therapy include the following:
Agents that may be considered for treatment of advanced-stage (stage IV) melanoma include the following:
Poor prognostic factors include the following:
Prognosis depends on the disease stage at diagnosis, as follows:
Patients with metastatic disease have a grim prognosis, with a 5-year survival rate of less than 20%.
Skin cancers are frequently seen by the primary care provider, nurse practitioner, internist, and the pharmacist. While many skin lesions are benign, it is important to always consider melanoma- as it is deadly if the diagnosis is missed. If there is suspicion of melanoma, the patient should be referred to the dermatologist/oncologist and pathologist for further workup. Surgery such as wide local excision with sentinel lymph node biopsy, elective node dissection, or both is the definitive treatment for early-stage melanoma. When performing the wide local excision, first consider the surgical margins. If the primary closure is not feasible, skin grafting or tissue transfers may be needed. Medical management is reserved for adjuvant therapy of patients with advanced melanoma. For localized lesions, the prognosis is with surgery but advanced melanoma has a grim prognosis. (Level V)
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