While uncommon, some skin cancers, particularly in early stages, can resemble a bruise. This potential for confusion highlights the importance of vigilance regarding skin changes. Understanding the characteristics of both bruises and suspicious lesions helps in recognizing when professional evaluation is needed.
What a Typical Bruise Looks Like
A bruise forms when small blood vessels beneath the skin are damaged. This causes blood to leak into surrounding tissues, becoming trapped and visible. Initially, a bruise appears red or purplish, reflecting fresh, oxygen-rich blood.
As the body reabsorbs the pooled blood, the bruise undergoes color changes. Within one to two days, it shifts to shades of blue, purple, or black as the blood loses oxygen. After five to ten days, the bruise turns green or yellow, indicating further breakdown of blood components. Finally, it fades to a yellowish-brown or light brown before disappearing entirely, a process that takes about two weeks.
Skin Cancers That Might Resemble Bruises
Some skin cancers can resemble a bruise, primarily due to their dark coloration or raised, firm nature. Nodular melanoma can appear as a rapidly growing, dome-shaped lump that is often firm. Its color ranges from black, blue-black, brown, or red, and it can also be skin-colored or appear like a blood blister or pimple. Its rapid vertical growth into the skin is a key feature.
Pigmented basal cell carcinoma can also cause confusion. It can present as a lesion with brown, blue, or black pigmentation, resembling a mole or melanoma. These lesions can appear as raised, shiny bumps, and may ulcerate or develop crusts.
How to Tell the Difference
Distinguishing between a bruise and a suspicious skin lesion involves observing several key characteristics. Bruises have a clear cause, such as an injury, and follow a predictable pattern of color changes and fading over a few weeks. In contrast, skin cancers persist beyond this timeframe, failing to heal or continuing to grow.
The evolution of the lesion is also a distinguishing factor. While bruises change color and gradually disappear, suspicious lesions can grow in size, change shape or color irregularly, or develop new symptoms like bleeding or itching. Bruises are tender or painful when fresh, but this tenderness subsides as they heal. Skin cancers are often painless, though they can become itchy, tender, or bleed as they progress.
Texture provides another important clue. Bruises are flat or slightly swollen, with smooth surfaces that flatten over time. Skin cancers can be raised, firm, scaly, or ulcerated, presenting with rough, shiny, or crusty surfaces. The borders of a bruise are diffuse and blend into the surrounding skin, whereas skin cancers can have irregular, notched, or poorly defined edges. Persistent bleeding, oozing, or non-healing sores are common signs of skin cancer but are not for a bruise.
When to Consult a Doctor
Seeking professional medical evaluation is important for any new, changing, or unusual skin lesion, particularly if it does not behave like a bruise. If a spot on the skin persists for more than a few weeks without signs of healing or fading, it requires medical attention. Any lesion that changes in size, shape, or color, or develops irregular borders, should be promptly evaluated.
Other concerning signs include a skin lesion that bleeds, itches, or is painful without a clear reason or history of trauma. If there is any uncertainty about a skin change, or if a lesion appears different from other moles or spots on the body, a dermatologist can provide an accurate diagnosis. Early detection of skin cancer is important for effective treatment outcomes.