Blanching refers to the temporary whitening of a spot on the skin when external pressure is applied. This effect occurs as blood is pushed out of the area, and the spot returns to its original color once the pressure is released. Understanding whether a skin lesion blanches is a common point of confusion when trying to determine if a spot might be a form of skin cancer. This article clarifies the relationship between blanching and malignant skin growths.
The Direct Answer: Skin Cancer and Blanching
The general answer is that skin cancer does not blanch when pressed, making the test an unreliable indicator for malignancy. Malignant lesions, such as melanoma, basal cell carcinoma (BCC), and squamous cell carcinoma (SCC), are solid masses of abnormal cells or highly concentrated deposits of pigment. Their color comes from the cellular structure or melanin within the cells, not primarily from blood in compressible vessels.
Relying on the blanching test can be misleading and may provide a false sense of security regarding a suspicious lesion. While a spot that does not blanch usually indicates fixed color, a lesion that does blanch is not automatically benign. Some skin cancers, particularly pink or red lesions, can present with a vascular component.
An exception is sometimes noted with certain pink lesions, such as amelanotic melanoma, which lack dark pigment. Highly vascularized or inflammatory lesions may show a slight color change, but this is not true blanching and is not a reliable diagnostic feature. A professional diagnostic technique for basal cell carcinoma involves stretching the skin over the lesion, causing the tumor to become more visible by turning white. This maneuver is used by professionals to aid visualization, not as a reliable self-test for malignancy.
Understanding the Mechanism of Blanching
Blanching is a physiological reaction driven by the temporary displacement of blood in the skin’s microvasculature. The skin’s red or pink color is largely determined by blood flowing through capillaries in the superficial layers of the dermis. When pressure is applied, it compresses these capillaries, forcing the blood out of the localized area.
As the blood is expelled, the underlying skin tissue briefly appears pale or white, creating the blanching effect. Once the pressure is lifted, blood rushes back into the vessels, and the normal color returns within seconds. This reaction confirms the color is caused by blood within a functioning, compressible vascular network.
Malignant tumors are composed of dense, proliferating cells that form a solid mass. For melanoma, the color comes from an accumulation of melanin pigment within the cancerous cells. When pressure is applied to these solid or pigmented structures, the color remains because the pigment or dense cellular material cannot be physically displaced like blood. The absence of blanching indicates the color is structural, which is why the test is associated with benign vascular lesions like hemangiomas, not cancerous growths.
Reliable Indicators for Skin Cancer Evaluation
Since blanching is not a dependable way to evaluate a spot, the established method for self-screening is the ABCDE rule. This framework helps identify the visual characteristics associated with melanoma, the most serious form of skin cancer.
The ABCDE rule consists of five criteria:
- Asymmetry: If a line were drawn through the middle of the lesion, the two halves would not match. Benign moles are typically symmetrical and round or oval.
- Border irregularity: Edges are often jagged, blurred, or notched, rather than smooth and well-defined. Cancerous borders appear ragged because the tumor grows irregularly into the surrounding skin tissue.
- Color variation: The lesion contains different shades, such as black, brown, tan, white, red, or blue. A harmless mole usually exhibits a uniform color throughout.
- Diameter: Any lesion larger than six millimeters (roughly the size of a pencil eraser) should be viewed with suspicion. This size serves as a helpful threshold for evaluation.
- Evolving: Refers to any change in the lesion’s size, shape, color, elevation, or any new symptom like bleeding, itching, or crusting. A lesion that changes over time is the most concerning indicator of a potentially serious malignancy.
While the ABCDE rule is primary for melanoma, other common skin cancers have distinct warning signs. Basal cell carcinomas often appear as a pearly, translucent, or waxy bump, sometimes with a depression in the center and visible blood vessels. Squamous cell carcinomas frequently present as a firm, red, scaly patch or an open sore that does not heal.
When to Seek Professional Evaluation
Any skin lesion exhibiting one or more of the ABCDE characteristics warrants an immediate appointment with a dermatology professional. The presence of a new, changing, or symptomatic spot should trigger a consultation, regardless of whether it blanches. Symptoms like persistent itching, tenderness, bleeding, or a sore that will not heal are concerning signs requiring expert attention.
A dermatologist will perform a thorough skin examination, often utilizing a specialized handheld microscope called a dermatoscope. This device allows the physician to visualize structures and patterns beneath the skin’s surface that are invisible otherwise. If the lesion remains suspicious after this examination, the next step is usually a biopsy.
A biopsy involves removing a small tissue sample for laboratory analysis to determine if cancerous cells are present. This procedure is the only way to definitively diagnose skin cancer. Early detection is a significant factor in successful treatment, making proactive monitoring and timely professional evaluation the most reliable strategy for maintaining skin health.