Excisional Skin Biopsy for Melanoma

Melanoma is a malignant tumor of melanocytes which are found predominantly in skin but also in the bowel and the eye. It is one of the less common types of skin cancer but causes the majority of skin cancer related deaths. Melanocytes are normally present in skin, being responsible for the production of the dark pigment melanin.

Around 60,000 new cases of invasive melanoma are diagnosed in the US 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.

Excisional skin biopsy is the management of choice for melanoma diagnosis; this is where the suspect lesion is totally removed with an adequate ellipse of surrounding skin and tissue. The preferred surgical margin for the initial biopsy should be narrow in order to prevent the disruption of the local lymphatic drainage.

The biopsy will include the epidermal, dermal, and subcutaneous layers of the skin, enabling the histopathologist to determine the thickness of the melanoma by microscopic examination. This is described by Breslow's thickness. 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. Thus, a small punch biopsy in representative areas will give adequate information and will not disrupt the final staging or depth determination.

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 would be enough. In no circumstances should the initial biopsy include the final surgical margin, as a misdiagnosis can result in excessive scarring and morbidity from the procedure.

Lactate dehydrogenase (LDH) tests are often used to screen for metastases, although many patients with metastases 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 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. 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. Some patients with metastatic melanoma do not have an obvious detectable primary tumor.

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 melanomas do not have pigment and may not even be visible. Lentigo maligna, a superficial melanoma confined to the topmost layers of the skin is often described as a 'stain' on the skin.

The treatment includes surgical removal of the tumor, adjuvant treatment, chemotherapy, immunotherapy, or radiation therapy.