Melanoma: Current Diagnosis, Initial Treatment, and Sentinel Lymph Node Biopsy

Background
Diagnosis
Tumor Microstaging
Prognosis
Initial Surgical Treatment (Wide-excision)
Surgical Treatment of Lymph Nodes
Sentinel Lymph Node Biopsy
For Additional Information / To Make an Appointment

Background

Malignant melanoma, or simply "melanoma" (since there is no benign form of the disease) is not a typical skin cancer but rather a malignant (cancerous) mole. It may arise from a preexisting mole (viz. a junctional or compound nevus) or from a single cell (the melanocyte) in an area of previously appearing normal skin.

The overall worldwide incidence of new cases of melanoma is increasing faster than any other cancer. Cure rates remain high, however. The likelihood of death from melanoma is declining, probably due to both earlier detection and improved therapy.

Diagnosis

In patients with a suspicious-appearing mole, the diagnosis of melanoma is established by biopsy. Depending upon size and location, the biopsy may remove all or part of the mole for pathologic evaluation.

Tumor Microstaging

Once the diagnosis of melanoma has been established, the tumor is carefully examined to determine how deeply it has grown into the skin. This degree of skin invasion is known as the "tumor microstage." The microstage has tremendous bearing upon type of treatment, prognosis, and survival, and is most often described in terms of Clark's level and Breslow thickness.

Clark's level

The skin has essentially five anatomic layers, or levels, from the outermost epidermis (level I) to the underlying fat (level V). Clark's level refers to deepest portion of the skin invaded by tumor, level I being preinvasive, level II thinly invasive, levels III-IV moderately invasive, and level V deeply invasive. Since overall skin thickness varies considerably throughout the body (e.g. eyelid skin versus heel skin), the level of invasion is more qualitative than quantitative.

Breslow thickness

This measurement, in millimeters (mm), is the actual thickness of the melanoma which is a reflection of the depth of penetration of the tumor into the skin. Tumors less than 1 mm thick (0-0.99 mm) are considered lower risk; those 1.0-3.99 mm are intermediate risk, and 4.0 mm or more are higher risk.

Most often both descriptors are used to define a melanoma (e.g. level III, 1.5 mm depth).

Prognosis

With proper surgical treatment, patients with melanomas of levels I, II or III with a thickness of less than 1.0 mm have an overall excellent prognosis with the overwhelming majority alive and well 5 to 10 years later. In this group of low risk patients the incidence of secondary disease spread to lymph nodes or other organs is rare. Patients with melanomas of levels III or IV, from 1.0-3.99 mm thick, are at intermediate risk for recurrence, particularly within nearby lymph nodes. Those with tumors of level V or 4.0 mm or more thickness - while still potentially curable - are at greatest risk for recurrence.

Various other factors beside tumor microstage also bear upon prognosis and survival. Favorable prognostic factors include female gender, younger age and tumors of the extremities. Less favorable risk factors are tumor ulceration, male gender, advanced age, and tumors of the head and neck or trunk. Least favorable factors are the presence of tumor cells within adjacent lymph nodes or spread to distant organs (such as the lung, liver, brain, bone).

Initial Surgical Treatment (Wide-excision)

Biopsy alone is not a treatment for melanoma and in the absence of additional therapy is associated with unacceptably high rates of local recurrence. The surgical removal of additional surrounding skin is necessary to reduce the risk of tumor regrowth, which is called "wide-excision."

The extent of additional skin removal, that is, the size of the wide-excision, is influenced by a multitude of factors, including tumor microstage (Clark's level and Breslow thickness), presence of ulceration, tumor location and patient age.

In general and where anatomically possible, melanomas less than 1.0 mm thick require at least 1 centimeter (cm) margins of wide-excision, while tumors 1.0 mm or more thick require removal of at least 2-centimeter margins of normal-appearing surrounding skin.

Wide-excision may reduce local recurrence to 3% or less.

Surgical Treatment of Lymph Nodes

The presence of melanoma in adjacent lymph nodes is often an intermediate phase of disease, prior to disease spread to other parts of the body. Lymph nodes (or lymph glands) function as filters and trap germs as well as cancer cells. These "gatekeepers" form one of the body's first lines of defense.

At the time of diagnosis of melanoma it is often difficult, if not impossible, to determine whether or not lymph node involvement has occurred since only a few cancer cells may have migrated to nearby lymph nodes. However, enlarged, firm lymph nodes virtually always contain melanoma and should be removed without biopsy. This is termed a "therapeutic lymph node dissection"; that is, removal of abnormal lymph nodes.

Lymph nodes that appear normal on physical examination may or may not contain melanoma, but are often removed as a preventive measure, termed a "prophylactic lymph node dissection" in patients with intermediate risk melanoma. Such removal is not of proven benefit, though several unconfirmed studies suggest 10-15% improvement in overall survival.

Sentinel Lymph Node Biopsy

Surgeons have recently discovered methods that may help determine whether or not small, normal appearing lymph nodes may contain melanoma cells, called "sentinel lymph node biopsy".

To be valid, this biopsy MUST BE PERFORMED PRIOR TO WIDE-EXCISION of the original melanoma. This biopsy technique uses radioactive particles and/or colored dyes injected into the previous melanoma biopsy site. This test often can determine which lymph node may be involved with tumor (i.e., the sentinel lymph node), thereby limiting the number of lymph nodes removed and thereby significantly reducing unnecessary surgery.

If the sentinel lymph node does not contain tumor cells, additional lymph nodes are not removed. Alternately, if the sentinel lymph node contains melanoma it is presumed that other lymph nodes in the area may also be contaminated with melanoma cells; in which case all nearby lymph nodes are removed (therapeutic lymph node dissection).

For Additional Information / To Make an Appointment

For additional information about melanoma, or to make an appointment at the UW Comprehensive Melanoma Clinic, please call (608) 263-8090.

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Plastic and Reconstructive Surgery - University of Wisconsin Department of Surgery
First published: 07/15/02 Last updated: 11/23/09 webmaster@surgery.wisc.edu
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