They are round or oval, feel flat or slightly elevated, like the scab from a healing wound, and range in size from very small to more than 2.5 centimetres (1 in) across.

[4] Visual diagnosis is made by the "stuck on" appearance, horny pearls or cysts embedded in the structure.

[10] Furthermore, thin seborrheic keratoses on facial skin can be very difficult to differentiate from lentigo maligna even with dermatoscopy.

[citation needed] A study examining over 4,000 biopsied skin lesions identified clinically as seborrheic keratoses showed 3.1% were malignancies.

[11] To date, the gold standard in the diagnosis of seborrheic keratosis is represented by the histolopathologic analysis of a skin biopsy.

[22] Onset is usually in middle age, although they are common in younger patients too, as they are found in 12% of 15-year-olds to 25-year-olds, which makes the term "senile keratosis" a misnomer.