Solar Lentigines (Age Spots)
"Senior spots" are medically known as solar lentigines, also called age spots, liver spots, or lentigo senilis. 1, 2
Definition and Characteristics
Solar lentigines are benign hyperpigmented macules that appear as light brown to black pigmented lesions of various sizes on chronically sun-exposed skin. 1, 3 These lesions occur in irregular shapes and are most commonly found on:
The lesions typically appear after age 50 and represent a common component of photoaged skin. 2
Underlying Cause
The primary cause is chronic exposure to ultraviolet (UV) radiation, particularly UVB radiation. 1 Solar lentigines serve as a marker of excessive cumulative sun exposure and are associated with increased risk for developing other forms of skin cancer. 1
Risk Factors Include:
- Fair skin, especially individuals who sunburn readily and tan poorly 1
- Proximity to the equator and higher altitude 1
- Environmental factors like reflective surfaces (water, snow, sand) 1
- Cumulative lifetime UV exposure, with more than half occurring during childhood and adolescence 1
Histological Features
Histologically, solar lentigines show elongated rete ridges with increased melanin at the tips, but importantly, the number of melanocytes is not increased. 2 Recent molecular studies suggest that increased proliferation of basal keratinocytes combined with decreased turnover of suprabasal keratinocytes leads to exaggerated rete ridge formation, which disrupts normal melanin processing. 3
Clinical Significance
While solar lentigines are benign lesions, they warrant attention because they can be difficult to distinguish clinically from melanoma in situ and junctional nevi. 4 There are documented cases of melanoma developing at sites previously diagnosed as solar lentigines. 4 However, some authors consider them potential precursors to seborrheic keratosis rather than melanoma. 2
The observation of possible association with melanoma development requires cautious assessment of these lesions. 2