A skin lesion is any abnormal change in the appearance or structure of the skin, ranging from simple color variations to raised, textured growths. Understanding the visual characteristics of these changes can offer helpful context but is not a substitute for medical expertise. Self-diagnosis based on images alone is unreliable and potentially dangerous. This article is intended for informational purposes only, and any new or changing lesion should be evaluated by a qualified healthcare professional, such as a dermatologist.
Categorizing Skin Lesions by Appearance
Skin lesions are broadly categorized by their morphology, which helps professionals classify the underlying process. The first category includes primary lesions, which arise directly from previously normal skin. Examples include macules, which are flat spots defined only by a change in color and are typically less than one centimeter in diameter. Raised, small, solid bumps less than one centimeter are called papules, while a plaque is a broader, flat-topped elevation greater than one centimeter, often formed by a collection of papules.
Fluid-filled lesions represent another type of primary change. Vesicles are small, raised blisters under one centimeter that contain clear fluid, while a bulla is a large vesicle measuring greater than one centimeter in diameter. A secondary lesion, in contrast, results from the evolution of a primary lesion, external trauma, or other factors that modify the original appearance.
Secondary changes include scales, which are visible flakes representing the shedding of the outermost skin layer. A crust, commonly known as a scab, forms when dried serum, blood, or pus collects on the surface of a lesion. An ulcer represents a full-thickness loss of the epidermis and dermis, which heals with scar formation, distinguishing it from an erosion that only affects the epidermis.
Identification Guide for Common Benign Lesions
The majority of skin lesions encountered are benign, representing harmless growths or pigment changes. Moles, or melanocytic nevi, are common benign growths that typically exhibit a uniform color, such as brown, black, or tan, with smooth, well-defined borders. They are generally symmetrical and remain stable in appearance and size over many years, distinguishing them from more concerning lesions.
Freckles (ephelides) and age spots (solar lentigines) are flat pigment changes correlated with sun exposure. Freckles are small brown macules, usually one to four millimeters in diameter, that darken with sun exposure. Solar lentigines are typically larger, tan to dark brown macules that appear in adulthood on sun-exposed areas, but maintain a uniform color and sharp border.
Skin tags (acrochordons) are soft, fleshy papules that are almost always pedunculated, meaning they hang from a small stalk. These growths are typically skin-colored and small, often found in areas of friction like the neck, armpits, or groin folds. Seborrheic keratoses are another frequent benign growth, appearing as warty plaques with a dull, waxy, or rough surface that gives them a characteristic “stuck-on” appearance. They can range in color from yellow to brown to black and often become more prevalent with age.
Warning Signs: When a Lesion Requires Immediate Attention
Recognizing specific changes in a lesion is important for the early detection of skin cancer, particularly melanoma, the most serious form. The ABCDE method provides a structured way to evaluate a pigmented lesion for signs of potential malignancy. A stands for Asymmetry, meaning the shape of one half of the lesion does not match the other half, unlike a typical benign mole.
B refers to Border irregularity, where the edges are uneven, scalloped, or notched, rather than smooth and clearly defined. C is for Color variation, indicating the presence of multiple colors or uneven shades within a single lesion (e.g., brown, black, red, white, or blue). D represents Diameter, as melanomas are often larger than six millimeters (roughly the size of a pencil eraser), though they can be smaller.
E stands for Evolving, referring to any change in the lesion’s size, shape, color, or elevation over time. Beyond malignancy, a lesion requires immediate attention if it shows signs of a severe acute issue, such as rapid growth or infection. Signs of a serious skin infection include increased pain, spreading redness and warmth around the area, pus draining from the lesion, or the onset of a fever.
The Professional Diagnostic Process
When a suspicious lesion is identified, a healthcare provider, often a dermatologist, begins the diagnostic process with a comprehensive patient history and visual inspection. The provider will ask about the lesion’s duration, any changes observed, and associated symptoms like itching or bleeding. A specialized handheld instrument called a dermatoscope is then used to perform a non-invasive examination of the lesion.
The dermatoscope provides magnification, typically up to ten times, and uses specialized lighting to visualize subsurface structures and patterns not visible to the naked eye. This enhanced visualization increases the accuracy in distinguishing between benign and malignant lesions, helping to triage which ones require further action. If the visual and dermoscopic evaluation suggests a risk of malignancy, a skin biopsy is performed.
A biopsy involves removing a small sample of the lesion, or sometimes the entire lesion, for laboratory analysis. This tissue sample is then processed and examined by a pathologist, who provides a definitive diagnosis by looking at the cell structure under a microscope. The pathology report confirms whether the lesion is benign, pre-cancerous, or malignant, guiding the next steps for treatment or monitoring.