Diagnosis: Solar lentigo
The woman had solar lentigines, or “liver spots.” These common, benign lesions result from melanocyte hyperproliferation secondary to chronic sun damage. They most frequently arise in older, fair-skinned individuals with an extensive history of sun exposure. Clinically, these oval, pigmented macules are uniform in color that can vary from tan to dark brown. The lesions are symmetrical, with a regular border and arise on sun-exposed skin, particularly on the face, chest, shoulders, and dorsal surfaces of the arms and hands.
The differential diagnosis includes seborrheic keratoses, lentigo maligna, and lentigo maligna melanoma. Early seborrheic keratoses often do not have the scale and palpable quality that would otherwise differentiate them from solar lentigo. Lentigo maligna is a melanoma in situ, a superficially spreading collection of atypical melanocytes, histologically confined to the epidermis. The nonpalpable quality, irregular borders, and uneven pigmentation of lentigo maligna are useful characteristics in making this diagnosis. Lentigo maligna melanoma is a cancerous lesion that has variable pigmentation. It is characterized by uneven borders and may have a nodular or papular component to it.
If the lesion has acquired a nodular or papular appearance or, for any other reason, seems worrisome, biopsy is suggested.1 In solar lentigo, increased numbers of atypical melanocytes occur in a single layer along the basal layer, above the basement membrane. Ordinarily, though, diagnosis is made clinically, and no biopsy or lab work is needed.
Solar lentigo requires no treatment, unless the patient desires it for cosmetic reasons. Liquid nitrogen applied to the site for five seconds or less can destroy the melanocytes. Prior to therapy, patients should be counseled that healing may be accompanied by hypopigmentation. Hydroquinone 4% cream can also lighten existing lesions. Sunscreen can prevent the formation of new lesions but cannot diminish the presence of existing ones.2 Patients should be educated on sunscreen use. A full skin exam should be done at each visit, as other effects of sun damage are often seen and skin cancers are a common finding.
Our patient, who had very pale skin (phototype I), was not concerned about possible hypopigmentation. On two consecutive visits, treatment of her face, hands, and forearms with liquid nitrogen yielded excellent cosmetic results.