Diagnostic Criteria
In most instances, the failure to correctly identify a given skin disease does not have life or death consequences. Melanoma constitutes one exception to this generalization. The prognosis in melanoma corresponds most directly with the depth of invasion, and this, in turn, relates at least in part to the duration of the lesion. Correct identification and early removal of superficial melanomas are associated with gratifyingly high cure rates, whereas failure to recognize a melanoma might well lead to a disastrous outcome. Any clinician would have great moral (and possibly legal) difficulty living with a misdiagnosis, but in spite of this consideration, evaluation of most pigmented lesions is carried out in a hurried and superficial manner. Biopsy of all pigmented lesions is not the answer. The cost in time and money is far too great when one considers that each of us has an average of about 15 pigmented nevi. The only practical approach is to develop our clinical skins to as great a degree as possible. A remarkably high degree of accuracy can be obtained when systematic criteria are used for evaluation.
Objective Criteria
Lesional Configuration. Most benign pigmented lesions are perfectly round. Melanomas, on the other hand, are often somewhat irregular in shape. This is sometimes termed lesional asymmetry; i.e., if a line were drawn through the center of a lesion and if the lesion were folded along that line, the two halves would not be superimposable. The earliest irregularity is often the appearance of a small area of pigment spread (pigment bleeding) onto the flat skin surrounding the lesion. More advanced change consists of one or more areas of irregular, peninsular growth of the elevated portion of the lesion. Some individuals, especially those of Celtic origin, will demonstrate some irregularity of configuration in almost all of their nevi. When multiple nevi are irregularly shaped, one should consider the possibility of the dysplastic nevus syndrome.
Surface Smoothness. Benign lesions generally have a smooth surface. Melanomas, on the other hand, sometimes show some irregularity of surface growth. The development of one or more “bumps” on the surface of a pigmented lesion suggests that clusters of the underlying cells may be growing at different rates. Thus, the presence of surface irregularity is analogous to the presence of configurational irregularity. It should be noted, however, that the absence of surface “bumpiness” does not argue against the diagnosis of a melanoma; early melanomas may be essentially flat with no areas of elevation.
Pigment Homogeneity. Most benign lesions are evenly colored throughout, whereas most melanomas show some variation in pigment density. For example, in a melanoma, one or more dark-colored speckles might be present against a lighter brown background. Some benign nevi, especially those of the dysplastic nevus syndrome, do show speckling of pigmentation, but a single speckled nevus when all others are more normal in appearance should arouse concern about the presence of a melanoma. It should be emphasized that only irregularity in density of pigment is important. Absolute density of pigmentation does not correlate with malignancy; benign lesions can be very black, and melanomas can be rather light.
Nonbroum Colors. Most benign pigmented lesions are brown or brown-black. Most superficial spreading melanomas have, in addition, red, white, or blue hues in various portions of the lesion. Those lesions that fall toward the notably red end of the brown spectrum should be considered as possible dysplastic nevi. White areas arc also quite important. These represent areas of pigment destruction from immunologic attack. Since benign pigmented lesions are ordinarily not recognized as foreign by the body, no immunologic reaction is directed against them. One important exception to this rule is the presence of a white halo that completely surrounds pigmented lesions. Such “halo nevi” are rather common in childhood and are invariably benign in nature. Halo nevi are not common in adults, and such lesions should be viewed with suspicion.
Presence of Inflammation. Inflammation does not spontaneously appear around benign lesions. The presence of such inflammation suggests that the body recognizes the lesion as foreign and is mounting an attack against it. In spite of the theoretical value of this sign, it happens that most inflamed pigmented lesions turn out to be benign nevi with small underlying ruptured epidermoid cysts.
Firmness on Palpation. Benign pigmented lesions feel quite soft when they are picked up between the thumb and forefinger. Firm lesions suggest that cellular proliferation is occurring at a rapid rate. Unfortunately, firmness is a finding noted primarily with malignancy of rather advanced stages.
Epithelial Disruption. Benign lesions never show evidence of spontaneous epithelial disruption. The presence of weeping, crusting, or ulcer formation in any pigmented lesion is a highly suspicious sign. On biopsy, however, many eroded pigmented lesions turn out to be benign nevi that have been scratched or otherwise traumatized.
Lesion Size. Large lesions are more suspect than small lesions. Melanomas are almost always larger in diameter than a lead pencil eraser (7 mm), whereas benign nevi, are congenital or dysplastic, are usually less than 7 mm in diameter.
Lesion Number. The likelihood of developing melanoma is linearly related to the number of pigmented lesions present. Individuals with more than 100 pigmented nevi almost always have at least several clinically dysplastic lesions and seem to be at especially high risk for eventual development of melanoma.
Subjective Criteria
Criteria that depend on patient history are inherently less accurate than the objective criteria. Nevertheless, several aspects of history may be helpful. The first has to do with the length of time the lesion has been present. Pigmented lesions that have been present from birth (congenital nevi) are more likely to undergo melanomatous degeneration than are nevi acquired in childhood. Likewise, newly acquired pigmented lesions after age 30 in adults are more suspect than those acquired in childhood.
The second important aspect of patient history has to do with the patient’s perception of change in a single lesion. An individual lesion described voluntarily and spontaneously by the patient as having changed in size, configuration, or pigment density should be viewed with considerable suspicion. Likewise, a single lesion described as recently becoming pruritic or painful should be examined with particular care. On the other hand, little importance can be attached to a patient’s comment that multiple lesions have changed or have become symptomatic.
Dysplastic Nevi
Dysplastic nevi and the dysplastic nevus syndrome cause special problems for all clinicians. There is no doubt that patients with numerous clinically dysplastic nevi and a family history of melanoma have a greatly increased risk for melanoma. This risk may be expressed by the transformation of existing dysplastic nevi into melanomas or by the development of de novo melanomas. Unfortunately, the magnitude of risk for those with clinically dysplastic nevi but who lack a family history of melanoma is not known with certainty. Common sense suggests that there is some increase in risk, but it can be argued that the actual risk is related to the total number of nevi present, which, in turn, perhaps relates to sunburn-type damage acquired in childhood. In any event, it seems expedient to offer patients with numerous clinically dysplastic nevi frequent and expert follow-up examinations.
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