Specific History


Common pigmented moles follow a defined evolution. At birth, only 1 to 2% of infants have an identifiable pigmented nevus. During the first decade of life, the number of moles increases rather slowly. At puberty and in the first half of the second decade, it is normal for this process to accelerate, and many new nevi appear. This proliferation often causes concern on the part of teenagers and their parents but is, in fact, a normal event provided the lesions themselves are clinically benign. New pigmented nevi also are common during pregnancy, and when combined with the physiologic darkening of preexisting moles during gestation, may cause patients to become unduly alarmed. All lesions of concern should be carefully evaluated and the patient advised and reassured.

Evolution of Disease Process and Skin Lesions

The common mole is composed of cells of neural crest origin, called nevus cells, which proliferate at the dermoepidermal junction, producing a benign neoplasm. Nevus cells have many of the properties of dendritic epidermal melanocytes but they also show distinctive morphological and functional differences. Like the dendritic melanocyte, they possess the organelles and enzyme systems to produce melanin pigment, which allows their presence to be distinguished from the adjacent epidermal surface. Unlike epidermal melanocytes, junctional nevus cells have an epithelioid-like appearance and lack den-drites.

The earliest stage in mole formation is a proliferation of nevus cells at the epidermal interface, which indents the epidermal base but does not raise, alter, or disturb its surface characteristics. The melanin produced defines the size and site of the lesion. Most acquired nevi in the first decade of life appear as small (5 mm or less) macular pigmented spots and are termed junctional nevi.

Some remain junctional for years, but in most instances the nevus cells continue to proliferate into the dermis and gradually push up on the overlying epidermis, effacing the skin lines or in some instances accentuating them. During this stage, the nevus will develop a raised component that may be visible and is definitely palpable. Nevus cells still form nests at the junction of dermis and epidermis, but with the added dermal component, this structure is now referred to as a compound nevus. This change, when it occurs in a gradual and orderly fashion, is reassuring and part of a benign evolutionary process. Compound nevi are typically dome-shaped with a smooth, shiny, or mammillated surface. As this maturation advances, the surface area of the nevus enlarges. In addition, the rate of pigment production in the dermal nevus cells may diminish; this combined effect often produces an overall lightening of the nevus. The effect is much like that seen when blowing up a red balloon. The balloon is still an even red, but the color has a lighter tint and appears more diluted due to the increased surface relative to the same amount of red pigment. The progression of moles from junctional to compound types may begin during the first decade of life and is usually firmly established by the middle of the second decade. This process continues well into middle life.

By the fourth and fifth decades, many nevi mature even further into dermal nevi. Within a dermal nevus, the cellular proliferation at the dermal-epidermal junction disappears and the nevus cells are predominantly, if not exclusively, intradermal. Dermal moles may be clinically indistinguishable from compound moles. With time, dermal nevi mature and often become flaccid, soft, and pedunculated. They may then resemble a common skin tag.

Nevi normally increase in number until the end of the fourth decade of life, when they reach a peak average of 43 per person in men and 27 per person in women of light skin type. There is considerable normal variation among individuals, and degrees of moliness are often consistent within family units. Heavily pigmented skin types have fewer moles per person. Except for the familial atypical mole syndromes (see section on atypical nevus syndromes, below), specific inheritance patterns and markers have not been determined. From the fourth decade of life on, nevi gradually undergo spontaneous resolution and mole counts of patients in their eighth decades of life and beyond are quite low. Most nevi resolve without a visible trace, while others fibrose into lesions clinically and microscopically indistinguishable from fibrous skin tags.

Provoking Factors

Puberty, pregnancy, and exogenous hormone administration have all been associated with rapid proliferation of nevocellular nevi. Mole-prone families usually exhibit greater numbers on sun-exposed skin with a relative paucity of nevi on covered and doubly covered regions. It is reported that heavy childhood sun exposure is a factor in the development of some moles.


Self-treatment is seldom a problem in regard to pigmented nevi.

Supplemental Review From General History

Personal and family history relative to malignant melanoma should be obtained when evaluating pigmented nevi. History regarding pregnancy and recent hormonal therapy may also be relevant. When evaluating facial nevi in female subjects, history regarding hair growth and attempts at plucking or removing hair from the mole may be important. Traumatic epilation of hair can produce benign inflammatory changes that are more easily confused with malignancy.

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