Managing Pigmented Skin Lesions: Early Detection and Diagnosis of Melanoma
The prognosis of a melanoma depends on early diagnosis and removal of the primary lesion before it can metastasize.
Patients with melanoma 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 0.75 mm in thickness are usually cured by the same procedure. But patients who have melanomas that are allowed to grow to 3 mm 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.
Incidence and Mortality
Melanoma is a tumor of melanocytes, the cells that contain melanin. Melanomas mostly arise in skin but can occur rarely on other mucosal surfaces and in the eye. Ocular melanoma is the most common cancer of the eye, with approximately 2,000 cases annually.
The incidence of melanoma has been rising over the past four decades. It is estimated that in 2015, there will be 73,870 new cases and 9,940 deaths in the United States.
Some of the predisposing factors for melanoma are:
- Fair skin.
- A family history or personal history of melanoma.
- Multiple nevi.
- Environmental exposures, such as pesticides.
Types of Melanoma
The four major types of melanoma are:
- Superficial spreading melanoma, the most common type, which is flat and irregular in shape and color.
- Nodular melanoma, which starts as a raised lesion that is dark with shades of blue and/or red. Some have no color and are known as amelanotic melanoma.
- Lentigo maligna melanoma, which usually occurs in the elderly in sun damaged skin. This type of melanoma is usually flat and tan and brown.
- Acral lentiginous melanoma, the least common form, which occurs on the palms, soles, or under nails (subunqual). It is more common in African Americans.
Pigmented Lesions Offer Several Danger Signs
The following criteria highlight important characteristics to consider when examining pigmented skin lesions:
- Asymmetrical shape.
- Border changes, such as irregular (notched or scalloped) edge, satellite pigmentation, erythema, or a depigmented halo that is irregular.
- Color variation, with either hyper- or hypopigmentation or the spread of pigment onto normal (flat) skin.
- Diameter enlargement beyond 4 mm to 6 mm.
- External surface changes, such as bleeding, ulceration, scaliness, crusting, or an elevated area in a previously flat lesion.
- Feeling of itchiness, tenderness, or pain.
An essential point is that a change in a pigmented lesion is always suspicious. Changes in benign nevi can 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’s 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. Whenever possible, an excisional biopsy is preferable.
- Dysplastic (atypical) nevi are larger and more irregular in shape than other types of 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 melanoma on clinical grounds alone. When considering this diagnosis, perform an excisional biopsy since a definitive diagnosis requires microscopic examination.
- Dysplastic nevi that present in large numbers may be a marker for increased risk of melanoma. Carefully follow patients who have many lesions 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 a 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 with unusual or atypical clinical features. 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 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 types of 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, an 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, biopsy the lesion. Anywhere from 20 percent to 50 percent of all melanomas begin in benign nevi, with the remainder arising in clinically normal skin.
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—studies that enable the determination of “sentinel” lymph nodes.
When a simple, complete excision is not practical, a partial biopsy is a reasonable alternative. Large, flat, pigmented facial patches suspected of being lentigo maligna and flat 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. With elevated lesions, shave biopsy is an alternative consideration. 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 pathological look-alikes can be difficult at times—even for experienced pathologists and dermatopathologists. Therefore, provide the pathologist with a complete clinical history.
The patient’s age is significant. While the clinically unusual benign spitz nevus may occur in children, it is uncommon over age 20. The size of the lesion is especially useful information if you send only a small or partial biopsy for evaluation. A pathologist will have a higher index of suspicion for a new 2 cm patch in a 50-year-old than for a 2 mm 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 been removed from the site of the present biopsy. Recurrent benign nevi can have microscopic features that simulate melanoma.
Because definitive pathologic diagnosis of melanocytic lesions can be difficult, when receiving an equivocal pathologic diagnosis, ask for a second opinion from an expert dermatopathologist. Underdiagnosing is obviously perilous. Overdiagnosing melanoma is also dangerous and can result in unnecessary treatment and patient anxiety.
Treatment and Classification of a Melanoma
Treatment starts with removal of the skin lesion and some surrounding tissue. Melanoma is classified clinically by the TNM system of the 2010 American Joint Committee on Cancer:
The depth of the tumor and invasion in the skin are evaluated using the Breslow scale and Clark levels. A treatment regimen is recommended from these measurements and an evaluation of the tumor using the TNM scale.
Sentinel Lymph Nodes
Lymphatic mapping by lymphoscintigraphy and intraoperative injection of radioisotope may be needed to evaluate lymph node involvement downstream from the tumor. Sentinel lymph node biopsy can be helpful in evaluating further treatment and the patient’s prognosis.
Chemotherapy, immunotherapy, and other innovative treatments are available for more advanced melanoma.