Melanoma (pronounced /ˌmɛləˈnoʊmə/ is a malignant tumor of melanocytes. Such cells are found predominantly in skin, but are also found in the bowel and the eye (see uveal melanoma). Melanoma is one of the less common types of skin cancer, but causes the majority (75%) of skin cancer related deaths. Melanocytes are normally present in skin, being responsible for the production of the dark pigment melanin. Despite many years of intensive laboratory and clinical research, early surgical resection of thin tumors still gives the greatest chance of cure.
Around 60,000 new cases of invasive melanoma are diagnosed in the United States each year, more frequently in males and in Caucasians. It is more common in Caucasian populations living in sunny climates than in other groups, or in those who use tanning salons. According to a WHO report about 48,000 melanoma related deaths occur worldwide per year.
The treatment includes surgical removal of the tumor, adjuvant treatment, chemo- and immunotherapy, or radiation therapy.
Excisional skin biopsy is the management of choice. Here, the suspect lesion is totally removed with an adequate (but minimal, usually 1 or 2 mm) ellipse of surrounding skin and tissue. In order not to disrupt the local lymphatic drainage, the preferred surgical margin for the initial biopsy should be narrow (1 mm). The biopsy should include the epidermal, dermal, and subcutaneous layers of the skin. This enables the histopathologist to determine the thickness of the melanoma by microscopic examination. This is described by Breslow’s thickness (measured in millimeters). However, for large lesions such as suspected lentigo maligna, or for lesions in surgically difficult areas (face, toes, fingers, eyelids), a small punch biopsy in representative areas will give adequate information and will not disrupt the final staging or depth determination. In no circumstances should the initial biopsy include the final surgical margin (0.5 cm, 1.0 cm, or 2 cm), as a misdiagnosis can result in excessive scarring and morbidity from the procedure. Large initial excision will disrupt the local lymphatic drainage and can affect further lymphangiogram directed lymphnode dissection. A small punch biopsy can be utilized at any time where for logistical and personal reasons a patient refuses more invasive excisional biopsy. Small punch biopsies are minimally invasive and heal quickly, usually without noticeable scarring.
Lactate dehydrogenase (LDH) tests are often used to screen for metastases, although many patients with metastases (even end-stage) have a normal LDH; extraordinarily high LDH often indicates metastatic spread of the disease to the liver. It is common for patients diagnosed with melanoma to have chest X-rays and an LDH test, and in some cases CT, MRI, PET and/or PET/CT scans. Although controversial, sentinel lymph node biopsies and examination of the lymph nodes are also performed in patients to assess spread to the lymph nodes. A diagnosis of melanoma is supported by the presence of the S-100 protein marker.
Sometimes the skin lesion may bleed, itch, or ulcerate, although this is a very late sign. A slow-healing lesion should be watched closely, as that may be a sign of melanoma. Be aware also that in circumstances that are still poorly understood, melanomas may “regress” or spontaneously become smaller or invisible – however the malignancy is still present. Amelanotic (colorless or flesh-colored) melanomas do not have pigment and may not even be visible. Lentigo maligna, a superficial melanoma confined to the topmost layers of the skin (found primarily in older patients) is often described as a “stain” on the skin. Some patients with metastatic melanoma do not have an obvious detectable primary tumor.