What are sunspots in medical terms?

Medical Definition of Sunspots

In medical terms, sunspots (solar lentigines) are benign, hyperpigmented lesions that occur on sun-exposed skin surfaces, primarily in middle-aged and elderly individuals, as a sign of photoaging and chronic accumulated sun exposure. 1, 2

Characteristics of Solar Lentigines

• Solar lentigines appear as brownish, flat lesions (often called "liver spots") on chronically light-exposed adult skin, commonly developing from age 30 onwards 1, 3
• They represent focal areas of abnormal keratinocyte proliferation and melanocyte hyperplasia, without melanocytic atypia or nests of melanocytes 4
• These lesions are most commonly found on sun-exposed areas such as the face, dorsa of hands, and other areas with chronic UV radiation exposure 5

Histopathological Features

• Histologically, solar lentigines show a 2-fold increase in melanocytes, a 2-fold increase in epidermal area, and a 2.2-fold increase in epidermal melanin content compared to normal photoexposed skin 4
• Facial solar lentigines often have a flattened epidermis (in about 49% of cases) rather than the rete ridge hyperplasia typically seen in lentigines from other anatomic sites 4
• In vivo reflectance confocal microscopy reveals structural deformation of dermal papillae, with the alignment pattern of hyperrefractive basal cells shifting from circular in non-lesional skin to irregular non-circular shapes in solar lentigines 3

Risk Factors

• The primary cause is chronic exposure to ultraviolet (UV) radiation, particularly UVB radiation 5
• Fair-skinned individuals are at higher risk, especially those who sunburn readily and tan poorly 5
• Environmental factors that increase risk include proximity to the equator, higher altitude, light cloud coverage, and reflective surfaces like water, snow, and sand 5
• More than half of a person's lifetime UV exposure occurs during childhood and adolescence, contributing to later development of solar lentigines 5

Clinical Significance

• While solar lentigines are benign, they can be difficult to distinguish clinically from junctional nevi or melanoma in situ, sometimes necessitating biopsy for definitive diagnosis 6
• They represent a marker of excessive sun exposure and are associated with increased risk for developing other forms of skin cancer 5
• Solar lentigines tend to progress over time, with studies showing increased deformation of dermal papillae, darkening of lesions, and enlargement over a 5-year period 3

Treatment Options

• Q-switched ruby laser treatment has shown successful results with high patient acceptance and low risk of adverse effects 1
• Combination therapy approaches include topical treatments (such as 2% mequinol/0.01% tretinoin), chemical peels, cryotherapy, and light-based therapies (IPL and lasers) 2
• Treatment is primarily for cosmetic purposes, as these lesions themselves have low malignant potential 1, 2

Prevention

• Prevention strategies align with general skin cancer prevention measures 5:
  • Minimize sun exposure during peak hours (10 a.m.–4 p.m.), especially the midday period (11 a.m.–1 p.m.) 5
  • Seek shade when outdoors during peak sun hours 5
  • Wear protective clothing, wide-brimmed hats, and sunglasses 5
  • Use broad-spectrum sunscreen (UV-A and UV-B protection) with SPF >15 5
  • Avoid artificial UV radiation from sunlamps and tanning beds 5