Pigmented Growths

Incidence

Freckles are a common incidental finding during a skin examination and are rarely a reason, in and of themselves, for seeking medical attention.

History

Freckles usually appear before 3 years of age and darken after ultraviolet (UV) light exposure. The patient has a history of sunburning easily.

Physical Examination

The freckled individual typically has a fair complexion and reddish or sandy hair. Hundreds of freckles occur on sun-exposed skin. They are 1 to 6 mm, irregularly shaped, discrete brown macules.

Differential Diagnosis

Lentigo and junctional nevus can look like a freckle. Actinic lentigo does not darken with sun exposure and is acquired later in life. In contrast, freckles darken after sun exposure and are present from early childhood. Lentigo simplex is acquired in childhood, but the lentigines are not confined to sun-exposed skin. Junctional nevi and freckles are acquired in childhood. Darker pigmentation and lack of change after sunlight exposure favor a diagnosis of junctional nevus.

Laboratory and Biopsy

Ordinarily, freckles do not require biopsy ( Fig. 6.1B ).

Therapy

Pathogenesis

Ultraviolet radiation induces an increase in melanin pigment in the basal layer of the epidermis without an increase in melanocytes.

Definition

A lentigo (plural, lentigines) is a brown macule caused by an increased number of melanocytes. Two types are recognized: lentigo simplex lesions arise in childhood and are few in number, whereas actinic (solar) lentigines ( Fig. 6.2 ) arise in middle age and are numerous in sun-exposed skin.

Incidence

Lentigo simplex is uncommon. Actinic lentigines are found on more than 90% of Caucasians after the age of 70 years, but seldom cause a patient to seek medical advice.

History

Lentigo simplex may be congenital or may arise in childhood. It has no relation to sun exposure. Conversely, actinic lentigo is acquired in middle age, does not fade, and occurs in sun-exposed skin. Patients often call actinic lentigo “liver spots.”

Physical Examination

Lentigo is a uniform, tan, brown, or dark brown macule. Lentigo simplex is sharply marginated and occurs anywhere on the body and mucosae. These lesions are usually few in number.

Actinic or solar lentigo is a tan or brown macule, ranging in size from several millimeters to several centimeters, with distinct borders. The lesion occurs in sun-exposed areas of the body: particularly on the dorsum of the hands, neck, head, shoulders, upper trunk, and lower legs.

Differential Diagnosis

In childhood, the differential diagnosis of lentigo includes junctional nevus and freckle . In adults, seborrheic keratosis and malignant melanoma in situ (lentigo maligna) are included in the differential diagnosis. The most important of these is lentigo maligna, which appears as an irregularly colored (varying shades of brown and black), irregularly bordered macule on sun-exposed regions of the body.

Laboratory and Biopsy

Biopsy is seldom indicated unless there is concern for a malignant melanoma. If biopsy is performed, the histologic picture is characterized by an increased number of melanocytes within the epidermis as well as increased pigmentation within the keratinocytes. The rete ridges may be normal or elongated ( Fig. 6.2B ).

Therapy

No therapeutic intervention is required, except for cosmetic purposes. For multiple actinic lentigo, tretinoin cream 0.1% (Retin-A) applied daily is effective in lightening these photo-aging spots. Irritation, however, is common, thus requiring less-frequent application (every other day or every third day) or use of a less concentrated cream (0.025% or 0.05%). Preparations containing hydroquinone are generally ineffective. A combination product, 2% mequinol plus 0.01% tretinoin solution (Solage) applied twice daily, lightens these spots. Mild freezing with liquid nitrogen or laser destruction of these pigmented lesions is effective. Sunscreens with a sun protective factor (SPF) of 30 should be used to prevent the development of more actinic lentigo.

Course and Complications

Lentigo has no malignant potential. The multiple lentigines syndrome , a rare but distinctive syndrome, is characterized by hundreds of lentigines on the trunk, head, and extremities, including the palms and soles. It is dominantly inherited and also called the LEOPARD syndrome ( L entigines, E lectrocardiographic abnormalities, O cular hypertelorism, P ulmonary stenosis, A bnormal genitalia, R etarded growth and development, and D eafness).

Peutz–Jeghers syndrome is a dominantly inherited trait that is distinctive because of numerous lentigines occurring around the mouth and eyes as well as on the lips, oral mucosa, hands, and feet, in association with gastrointestinal polyps. Intussusception, hemorrhage, and malignancy are complications of these polyps.