About malignant melanoma
Malignant melanoma is a malignant neoplasm comprised of melanocytes and nevus cells, both of which are pigment-producing. It is typified by irregularity in shape and color, and eventually a palpable papule or plaque. There are four types of malignant melanoma: superficial spreading, lentigo maligna, nodular, and acral lentiginous.
Lentigo maligna melanoma. This form usually occurs in sun-exposed areas, such as the head and neck, and most frequently occurs in the elderly (median ~70 yrs old). It is multicolored and variably elevated in some areas. It is preceded by in situ melanoma, or lentigo maligna.
Superficial spreading. This is the most common form of melanoma. It is not associated with sun-exposed surfaces, and can often be found on the back or legs. Median age of onset is ~50 years. It is irregular in color, border, and surface texture.
Nodular. This form occurs on all skin surfaces, with a median age of onset of ~50 years. It is a rapidly growing, blue-black nodule, that may be eroded.
Acral lentiginous. This form occurs on the palms and soles and, in contrast to the other forms, occurs most frequently in Blacks and Asians. It has a median onset of ~60 years of age. It has irregular borders and a black color.
With what can malignant melanoma be confused?
Lentigo maligna melanoma can be confused with actinic lentigo or, sometimes, seborrheic keratosis. A superficial spreading melanoma can resemble pigmented basal cell carcinoma or a nevus or, less often, seborrheic keratosis or angioma. Nodular melanoma can be confused with blue nevus (a blue nodule that begins in childhood), pyogenic granuloma, angioma, or dermatofibroma. The acral lentiginous variety can mimic a nevus or a rare fungal infection termed tinea nigra palmaris.
How is malignant melanoma diagnosed?
A new pigmented lesion, or one that increases in size or changes color, areworrisome signs that often prompt patients to seek medical care. Other suspicious signs are bleeding or itching of a pigmented lesion. Some patients have a family history of melanoma, prompting increased scrutiny. Your dermatologist may examine the lesion with a special lens called a dermatoscope to aid in diagnosis. The classic ABCDEs of melanoma detection are asymmetry, border irregularity, color variegation, diameter greater than 6 mm, and evolving, or changing in size, shape or color. However, not all malignant melanomas follow the ABCDE rules; any suspicious pigmented lesion should be examined by biopsy, excisional when possible, with 2 to 3 mm margins. If the lesion is large, such as often occurs with lentigo maligna melanoma, incisional biopsy is acceptable.
How is malignant melanoma treated?
Excision is the treatment of choice when melanoma is detected early. The required margin is determined by the depth of cancer invasion, with deeper lesions requiring wider margins. The surgeon may perform sentinel lymph node mapping, in which a tracer is injected in to the lesion to determine the first draining lymph node. This node can then be examined to determine whether malignant cells have spread. The potential benefit of lyphadenectomy is determined by the stage of the cancer. If the melanoma has metastasized, chemotherapy and/or immunotherapy is required; excision will not be curative. Melanoma is treated by specialists including a surgeon and an oncologist. Frequent follow-up is required. Melanoma vaccines are still in the research and development stage.
What is the prognosis for malignant melanoma?
The lentigo maligna, superficial spreading and acral lentiginous types of melanoma have a “horizontal” growth phase, during which the lesion is flat or slightly raised. The lesion is completely curable by excision during this phase, and prognosis is directly related to the thickness of the tumor, ranging from a 5 year survival of 99% to 22% . Therefore, early detection is crucial. Nodular melanoma unfortunately only has a “vertical” growth phase.
How is malignant melanoma prevented?
Sunlight is likely a risk factor in some types of melanoma, as is family history. A large number of small nevi, large nevi, or dysplastic nevi are also risk factors. Prudent avoidance of sunlight irradiation is always recommended. Close physician follow-up for patients with risk factors is recommended, with the exact frequency determined by the risk factors and prior duration of follow-up.
