What is the medical term for a sunspot on the skin, also known as a liver spot, in individuals with a history of significant sun exposure?

Solar Lentigo

The medical term for a sunspot on the skin is "solar lentigo" (plural: solar lentigines), also commonly referred to as "liver spots" despite having no relationship to liver function. 1, 2

Definition and Terminology

Solar lentigines are benign pigmented lesions that develop on chronically sun-exposed skin as a direct result of cumulative ultraviolet (UV) radiation exposure, particularly UVB radiation. 1 The term "liver spot" is a misnomer that persists in common usage but has no pathophysiologic basis. 2

Clinical Characteristics

Solar lentigines appear most commonly on sun-exposed areas including:

• Face 1
• Dorsa of hands 1
• Other chronically UV-exposed body regions 1

The lesions are typically darkly pigmented macules with well-defined borders, though a variant called "ink spot lentigo" or "reticulated black solar lentigo" presents with markedly irregular, wiry or beaded borders and intense black pigmentation. 3, 4

Pathophysiology and Risk Factors

Key risk factors include:

• Fair skin that sunburns readily and tans poorly 1
• Chronic UV radiation exposure, with more than half of lifetime UV exposure occurring during childhood and adolescence 1
• Environmental factors such as proximity to equator, higher altitude, and reflective surfaces (water, snow, sand) 1

Histologically, solar lentigines demonstrate lentiginous hyperplasia of the epidermis with a twofold increase in both melanocytes and epidermal melanin content compared to normal photoexposed skin. 5 Facial solar lentigines frequently lack the classic rete ridge hyperplasia seen at other anatomic sites and may have flattened epidermis. 5

Clinical Significance

Solar lentigines are biomarkers of significant cumulative UV damage and indicate elevated skin cancer risk. 1, 6 They are associated with increased risk for developing squamous cell carcinoma, basal cell carcinoma, and melanoma. 1, 6 Fair-skinned individuals with multiple lentigines warrant annual full-body skin examinations at minimum, with consideration for surveillance every 3-6 months given their high-risk profile. 6

Important Clinical Pitfall

While solar lentigines are benign, distinguishing them from melanoma in situ can be challenging in clinical practice, particularly on sun-damaged facial skin. 2 The ink spot lentigo variant, with its dark color and irregular borders, is frequently mistaken for melanoma despite being benign. 4 Any changing, irregular, or symptomatic pigmented lesion requires dermatology evaluation and should not be dismissed as a simple "age spot." 6