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Regular skin exams can identify suspicious lesions, but an accurate diagnosis requires a biopsy. During the biopsy, a doctor will inject a local anesthetic in the area of the lesion and then remove a sample of the lesion (sometimes the entire lesion) and send it to a laboratory for analysis.

In most cases, a doctor will perform an to remove tissue for examination. Several types of excisional biopsies are used for melanoma diagnosis: deep-shave technique (also called saucerization); elliptical (full thickness); or punch biopsy, which involves removing a piece of tissue with a hand-held device.

Most studies have shown that the type of biopsy does not affect diagnostic accuracy or clinical outcomes. In some cases, usually involving flat skin lesions, a doctor may perform an incisional biopsy, which is a smaller procedure that involved less tissue.

When examined through a microscope, melanoma cells have a distinct makeup and distribution that distinguish them from normal skin cells and from benign growths, such as moles and warts. Pathologists are trained to recognize the differences and determine whether a lesion is malignant or benign.

Pathology Report

The pathologist summarizes the findings from a biopsy in a report for the doctor who performed the biopsy. If the skin lesion is not cancerous, the report will include details about the cellular makeup and distribution of the cells and describe the type of skin lesion associated with those features.

If the findings indicate melanoma, the report will include information about how advanced the cancer is and about factors that influence the likelihood that the melanoma will progress or spread. The features below will be included in the reports if noted:

• Breslow thickness -- The measured thickness of the melanoma and how far it extends into the skin

• Ulceration -- Breakdown of skin on the melanoma, a marker of increased risk

• Mitotic rate -- A measure of how fast the cancer cells are growing and dividing

• Margin status -- How close the cancer cells are to the edges of the biopsy

• Microsatellites -- Microscopic clusters or nests of tumor cells that can be seen or felt as a nodule near the primary tumor

• In-transit melanoma -- Cell clusters that have migrated farther from the primary lesion but have not reached a lymph node

Pathologists include what they consider to be the essential information about a melanoma lesion, and that can vary from one pathologist to another. Additionally, treating physicians may request specific types of information. Patients should talk with their doctors about the information in a pathology report and about how to interpret the information.

Types of Melanoma

Melanoma has several that are defined by the specific types of cells that make up the lesion. Some pathologists and other doctors consider this essential information, and it may be included in the pathology report.

• The most common subtype is superficial spreading melanoma, often found on the chest, abdomen, and legs. About 70% of all melanomas fall into this category

• The next most common is nodular melanoma (15-20% of lesions), which tends to grow quickly and accounts for about half of all melanoma deaths. The lesion often appears as a large black bump that resembles a mole, bug bite, or pimple. These types of lesions tend to arise on skin areas that have a lot of sun exposure: the legs, torso (including the back), arms, and head

• Pure desmoplastic melanoma (less than 5% of lesions) is a firm, plaque-like lesion and often occurs on the face, shoulders, or scalp. The lesions tend to be thicker than superficial spreading melanomas and are associated with an increased risk of recurring in the skin

• Acral lentiginous melanoma is another uncommon subtype and arises in unusual locations, such as the soles of the feet, palms of the hands, fingertips, and under the nails. This subtype occurs more often in dark-skinned individuals

• Lentigo maligna is a superficial lesion that typically appears as an irregular brown patch on the head or neck and is associated with chronically sun-damaged skin. When deeper penetration into the skin occurs, physicians may refer to the lesion as lentigo maligna melanoma

Disease Stage

The melanoma stage at diagnosis represents how far the lesion has penetrated into the skin and whether it has spread away from the primary tumor to lymph nodes or other organs.

Stage 0 (often described as melanoma in situ) is limited to the skin surface.

Lesions that are stages I or II have penetrated below the surface but remain in the uppermost levels of the skin. Stages I and II are further subdivided on the basis of melanoma thickness and other factors that are associated with an increased risk of becoming more invasive or advanced.

Stage III melanoma (also called locally advanced) has spread to one or more lymph nodes or the surrounding tissue often leading to the closest lymph nodes. The stage is subdivided into stages IIIA through IIID, according to the melanoma's thickness, presence or absence of ulceration, number of lymph nodes affected, presence of microsatellites or in-transit disease, and other factors that determine the risk of continued progression.

Stage IV means that the disease has spread beyond the primary tumor and lymph nodes to other organs in the body.

Imaging and Laboratory Tests

In general, imaging studies (x-ray, CT, MRI) and laboratory tests have little role in the initial diagnosis of primary melanoma. They play a more prominent role in planning treatment and determining response to treatment for patients with stages III and IV disease. Similarly, tests for genetic mutations in the tumor play a greater role in determining the type of medical treatment that might be used for melanoma, particularly for patients with stage IV (metastatic) melanoma, for which surgery is usually not recommended.

Read previous installments in this series:

Part 1: For Your Patients: What Is Melanoma?

Part 2: Is What You're Seeing Harmless or Is It Melanoma?

"Medical Journeys" is a set of clinical resources reviewed by doctors, meant for physicians and other healthcare professionals as well as the patients they serve. Each episode of this 12-part journey through a disease state contains both a physician guide and a downloadable/printable patient resource. "Medical Journeys" chart a path each step of the way for physicians and patients and provide continual resources and support, as the caregiver team navigates the course of a disease.