2. What are the primary lesions that you would expect to find in solar lentigines?

27 ^Lentigines

CLINICAL APPLICATION QUESTIONS

A 44-year-old man requests evaluation of an irritated brown lesion on his left shoul- der. Evaluation reveals a typical 5-mm “stuck on” seborrheic keratosis. He also has mul- tiple lentigines of various sizes in a solar distribution over his upper back, shoulders, and upper chest. An asymmetric multicolored 4 × 8 mm lesion is present on his left anterior shoulder. It has a notched margin and stands out from the other lesions.

1. Should the multicolored lesion be biopsied?

2. What are the primary lesions that you would expect to find in solar lentigines?

3. What are the secondary lesions that you would expect to find in solar lentigines?

4. What should you tell the patient about the solar lentigines?

5. Is there any relationship between lentigines and melanoma?

6. How are solar lentigines treated?

APPLICATION GUIDELINES Specific History

Onset

A lentigo is a focal area of numerically increased, but benign, nonproliferating melanocytes at the dermoepidermal junction. There are two common types: small nonso- lar lentigines and larger sun-induced lentigines. Most nonsolar lentigines arise during the first decade, but they may increase in number into adulthood or occasionally arise later in life. Solar lentigines begin in the second decade of life, except with intense solar exposure, when they may appear even earlier.

Evolution of Disease Process and Skin Lesions

Once present, nonsolar lentigines are quite stable. They do not change in color or number with solar exposure. Spontaneous disappearance has been recorded. This type of lentigo is usually dark brown and tends to be more discrete, symmetrical, and less densely grouped than ephelides. They show fewer tendencies toward confluence. Even confluent lentigines rarely exceed 0.5 cm in size.

A solar lentigo is microscopically identical to its nonsolar counterpart. This type is usually 0.5 to 1 cm or more in size and appears after acute or chronic sun exposure. The margins are irregular, but like nonsolar lentigines, the normal skin lines can be readily fol- lowed across the lesion’s surface. Both are absolutely macular.

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From: Current Clinical Practice: Dermatology Skills for Primary Care: An Illustrated Guide D.J. Trozak, D.J. Tennenhouse, and J.J. Russell © Humana Press, Totowa, NJ

246 Part V / Malignant Skin Diseases

Provoking Factors

Nonsolar lentigines have no provoking factors. The stimulus for solar lentigines is intense ultraviolet light exposure.

Self-Medication

Self-treatment is not a problem.

Supplemental Review From General History

The presence of widespread small nonsolar lentigines may signal one of the rare mul- tisystem syndromes, such as Leopard, Lamb, or Name syndromes. Periorificial and oral mucous membrane lesions may be a sign of Peutz-Jeghers syndrome. Appropriate histor- ical review and exam are then indicated.

Dermatologic Physical Exam Primary Lesions

Nonsolar lentigines: These are macules of medium to dark-brown pigmentation that retain normal skin markings over their surface. Even when confluent, their size rarely exceeds 5 mm. They may be clinically indistinguishable from a junctional nevus. They are generally darker, sharper, and more regular than ephelides (see Photo 5).

Solar lentigines: These are macules of light- to medium-brown pigmentation tht retain normal skin markings over their surface. Color is often uneven, and the margins are irregular and fuzzy. Size varies from 0.5 to 1 cm or more (see Photo 6).

Secondary Lesions None with either type.

Distribution

Microdistribution: None with either type.

Macrodistribution: Nonsolar lentigines may be randomly present anywhere on the skin or mucous membranes. Solar lentigines may be seen in areas of intense sun exposure, especially in youths who sunburn easily. Face, upper back, and shoulders are common loca- tions. These are also common in adults after chronic exposure, usually in their fifth decade or older. Facial eminences and dorsum of hands are the most common sites (see Fig. 2).

Configuration

None with either type.

Indicated Supporting Diagnostic Data

None, unless irregularity or size suggests another more aggressive type of pigmented lesion. In this case, dermatologic consultation or a diagnostic biopsy may be prudent.

Therapy

In general, no therapy other than an explanation and reassurance is indicated. On

occasion, specific cosmetically bothersome lesions can be removed, but the practitioner

must carefully balance the benefits against any potential scarring. Cryotherapy with LN

is often successful with the solar type, but mild scarring and residual hypopigmentation can result. The patient must be forewarned. In some locations, such as the vermilion of the lip, punch excision gives an acceptable result. With invasive removal, site and skin type must be carefully assessed. A recent report cites solar lentigines as a significant inde- pendent risk factor for malignant melanoma. The risk factor is significant enough to war- rant a total body pigmented-lesion check, instruction on monthly self-exam, and yearly follow-up.

Conditions That May Simulate Lentigines Junctional Nevi (Moles)

A benign nonsolar lentigo may be absolutely indistinguishable on clinical exam from a benign junctional nevus. Unless either lesion is irregular or changing, the distinction is

Figure 2: Macrodistribution of solar lentigines.

248 Part V / Malignant Skin Diseases academic. Solar lentigines are larger and more irregular, and are not easily confused with nevi.

Ephelides

Benign nonsolar lentigines may be difficult to distinguish from ephelides. These lentig- ines tend to be more sparse and scattered than ephelides and are generally darker in color.

In addition, they do not darken or multiply with sun exposure and show little tendency to become confluent. Solar lentigines are larger and are not easily confused with ephelides.

Seborrheic Keratosis

Solar lentigines and early SKs in older persons may be hard to distinguish. The SK will, on close inspection, show a subtle raised “stuck-on” appearance and a dull surface.

The lentigo will retain the normal skin markings and light reflectance.

Actinic Keratosis

Solar lentigines and pigmented AKs are also hard to distinguish. The AK usually has a scale that is clinically evident or can be raised with light scraping. Like the SK, its sur- face is dull due to disordered surface formation.

Lentigo Maligna

Solar lentigines may enter into the differential diagnosis of this type of in situ malig- nant melanoma seen in older persons. Both lesions occur in similar solar-exposed areas and both are irregularly shaped areas of macular pigmentation. In general, lentigo maligna is a much larger and more irregular lesion, and shows irregular tan, brown, and dark- brown pigment within a given lesion. Most benign lentigines tend to be about 1 cm or less in size and show uneven tan pigment.

ANSWERS TO CLINICAL APPLICATION QUESTIONS History Review

A 44-year-old man requests evaluation of an irritated brown lesion on his left shoul- der. Evaluation reveals a typical 5 mm “stuck on” seborrheic keratosis. He also has mul- tiple lentigines of various sizes in a solar distribution over his upper back, shoulders, and upper chest. An asymmetric multicolored lesion 4 × 8 mm is present on his left anterior shoulder. It has a notched margin and stands out from the other lesions.

1. Should the multicolored lesion be biopsied?

Answer: The multicolored lesion may be a melanoma, and conservative exci- sional biopsy is indicated.

2. What are the primary lesions that you would expect to find in solar lentigines?

Answer: Light to medium-brown macules that retain normal skin lines. Color is

often uneven. Usually the lesions are 5 to 10 mm in size but occasionally may be

slightly larger.

3. What are the secondary lesions that you would expect to find in solar lentigines?

Answer: Usually none.

4. What should you tell the patient about the solar lentigines?

Answer: Widespread solar lentigines are the result of chronic sun exposure, and generally are not treated. The patient should be warned about a small increased lifetime risk of melanoma, and should be counseled regarding sun avoidance, pro- tective clothing, and use of sunscreen. Monthly self-examination based on the ABCD (Asymmetry, irregular Borders, variegated Coloration, large Diameter) system should be advised along with yearly office follow-up and immediate fol- low-up for a changing lesion.

5. Is there any relationship between lentigines and melanoma?

Answer: Large numbers of solar lentigines have been reported as a significant independent risk factor for malignant melanoma. There is no established relation- ship between nonsolar lentigines and melanoma.

6. How are solar lentigines treated?

Answer: Generally solar lentigines are not treated.