Managing Pigmented Skin Lesions: Early Detection and Diagnosis of Melanoma

The prognosis of melanoma depends on early diagnosis and removal of the primary lesion before it can metastasize.

Patients with melanomas confined to the epidermis (melanoma in situ) can be cured by a simple excision with conservative margins.

Patients with invasive melanomas that are less than 0.75mm in thickness are usually cured by the same procedure. But patients who have melanomas that are allowed to grow to 3mm in thickness have a dire prognosis: Fewer than half live for five years. Early recognition and excision of the primary lesion are therefore critical to improving survival.

The lifetime risk of developing a melanoma is skyrocketing in the United States; it has risen from 1:1,500 people in 1953 to nearly 1:100 in 1996. Much of the increase can be attributed to early detection and changed pathologic criteria for diagnosis, however, a definite increase in mortality as a result of melanoma is occurring.

Increased awareness of the frequency of melanoma by physicians and patients is also critical to reducing the mortality rate. Neville Davis, M.D., director of the Queensland Melanoma Project in Australia, identified early detection as the key to his team’s successful effort to reduce melanoma mortality.

"If individuals are instructed to report any change in a mole," he said, "and if physicians are alert to the possibility of melanoma, the diagnosis can be made at an early biological and possibly curable stage. In Queensland, Australia, there are few major cancers that have as hopeful a prognosis."

Clinical Diagnosis

The accuracy of clinically diagnosing melanoma is about 50 percent. A variety of pigmented skin lesions, from seborrheic keratoses to melanocytic nevi of various types, can simulate melanoma, and many melanomas have a deceptively bland clinical appearance. Diagnosis must be confirmed by pathologic examination. Physicians should be very suspicious of pigmented lesions; when in question, these lesions should be biopsied.

The person who typically develops melanoma is a light-skinned, blue- or green-eyed Caucasian who is increasingly of the middle or upper class. Freckles, inability to tan, and easy susceptibility to sunburn are all markers of increased risk. Physicians should be more suspicious of pigmented skin lesions on patients with this coloring; again, when in question, these lesions should be biopsied. Anywhere from 20 percent to 50 percent of all melanomas begin in benign nevi, with the remainder arising in clinically normal skin.

Pigmented skin lesions offer several danger signs:

• asymmetrical shape
• border changes, such as irregularity (notched or scalloped edge), satellite pigmentation, erythema, or a depigmented halo that is irregular
• color variation—either hyper- or hypopigmentation or the spread of pigment onto normal (flat) skin
• diameter enlargement beyond 4mm
• any new pigmented lesion greater than 6mm
• external or surface changes such as bleeding, ulceration, scaliness, crusting, or an elevated area in a previously flat lesion
• feelings of itchiness, tenderness, or pain

An essential point is that change in a pigmented lesion is always suspicious. Changes in benign nevi evolve in an imperceptibly slow manner. Any sudden change should prompt immediate attention.

Many melanomas arise in nevi, thus several types merit review:

• Nevi—range from small lesions of less than a centimeter across to giant lesions that may cover much of a limb or the entire trunk. The risk of a patient developing a melanoma in a giant nevus needs to be emphasized. Follow nevi for changes and promptly excise small lesions or biopsy the changed area within a large nevus.
  
  
• Dysplastic nevi—or atypical moles, are larger and more irregular in shape than other types of acquired melanocytic lesions. Often, dysplastic nevi have a pink periphery and a tan or brown, slightly elevated center. A dysplastic nevus can be exceedingly difficult to distinguish from an in situ or thin melanoma on clinical grounds alone. If you have anyquestion about the diagnosis, perform an excisional biopsy.
  
  Dysplastic nevi that present in large numbers may be a marker for increased risk of melanoma. Follow patients with many lesions carefully for the development of melanoma both within a nevus and in clinically normal skin. If a family member with numerous dysplastic nevi has a history of melanoma, the risk of melanoma in other family members with many such nevi may approach 100 percent.

Managing the Pigmented Lesion

It is exceedingly important to maintain a high index of suspicion and to biopsy any pigmented skin lesions that present a reasonable risk of melanoma. The same is true for any pigmented lesions that the patient says have changed. Examination under good lighting is important, and a magnifying light is helpful.

The best way to biopsy most pigmented skin lesions is by a simple, complete excision. The advantages of this technique are two fold. First, pathologic examination of melanocytic neoplasms depends in part on ascertaining architectural features such as symmetry and circumscription. These attributes cannot be evaluated if the lesion is transected. Second, even if the diagnosis of melanoma is missed pathologically, many melanomas may be cured by excision with free margins of only a few millimeters (although this is obviously not optimal for known melanomas).

Simple, complete excisions are best performed with a scalpel. Closing a wound that extends into the subcutis is far easier than closing one that extends only into the deep dermis. An alternative to simple, complete excision is a deep shave biopsy, sometimes referred to as shave excision or saucerization. In this technique, the entire lesion and a few millimeters of clinically normal skin are removed by using a scalpel held at a slight angle to the skin surface. Because melanocytes of a nevus or melanoma can extend beyond the clinically evident lesion, it is best to score the surface of the skin with a scalpel prior to beginning the shave. Use the scored lines as a guide to the final dimensions. Partial shave biopsies can lead to pathologic misdiagnosis and can render complete evaluation of a melanoma’s prognostic attributes impossible.

Simple, complete excision is also the best technique for removing a lesion that is believed to be a melanoma. Many clinicians try to spare the patient additional surgery by performing definitive treatment (excision with wide margins) without a pathologically confirmed diagnosis of melanoma. Because many unusual benign neoplasms simulate melanoma clinically, many seborrhea keratoses, compound melanocytic nevi, and other innocuous lesions have been excised with wide margins to the detriment of patients. Wide excision can also compromise studies to determine lymphatic drainage, which enable the determination of "sentinel" lymph nodes.

When a simple, complete excision is not practical, a partial biopsy is a reasonable alternative. Large, pigmented facial patches suspected of being lentigo maligna and lesions on genital skin or weight-bearing areas of the foot are examples of conditions where complete excision of a benign lesion might result in a cosmetic or functional defect. In such cases, a punch biopsy, or several punch biopsies, may be informative without causing harm. It is important to remember that a partial biopsy does not provide information about what is present in the remainder of the lesion. If the lesion has several areas of clinically different appearance, obtain several biopsies. If any of the biopsies are suspicious, complete excision with conservative margins would be appropriate. The thickest part of a lesion should be punched only if the biopsy will go through the entire thickness of the neoplasm; if the lesion proves to be a melanoma, prognostic evaluation is largely based on a reliable measurement of its maximum thickness.

Pathological Examination of the Pigmented Lesion

Distinguishing between melanoma and its pathologic look-alikes can be difficult at times—even for experienced pathologists and dermato-pathologists. Therefore, provide the pathologist with as complete a clinical history as possible. The patient’s age is significant. While many unusual benign lesions occur in children, few junctional nevi or Spitz nevi occur in older adults. The size of the lesion is especially useful information if you send only a small biopsy for evaluation; a pathologist will have a much higher index of suspicion for a new 2cm patch in a 50- year-old than for a 2mm macule in a 20-year-old. A history of change is also important information. The pathologist may need to serially section the specimen until an explanation for the change is found. The reason for such changes in nevi can range from folliculitis to a small focus of incipient melanoma. The pathologist must also know if a lesion has previously been removed from the site of the present biopsy. Recurrent nevi can have features that simulate melanoma under the microscope and are yet benign.

Because pathologic examination of melanocytic neoplasms is so difficult, obtain expert consultations in the case of questionable lesions. Underdiagnosing is obviously perilous. Overdiagnosing melanoma, just to be safe, is dangerous as well, as unnecessary treatment and anxiety can result. Diagnosis should not err one way or another, but should be as accurate as possible.

J3225 5/00

Updated: May 2000
Originally published: February 1995