It is a common concern whether the hair itself can develop cancer, especially when noticing changes on the scalp. The direct answer is no; cancer cannot originate in the visible hair shaft, which is the part extending above the skin. However, the living tissues of the scalp and the hair follicle structures beneath the surface are susceptible to various forms of skin cancer. Understanding the difference between the non-living hair strand and the surrounding active cells of the scalp is important for recognizing the real risks in this area.
The Biological Reality: Why Hair Itself Cannot Get Cancer
The reason the visible hair strand cannot become cancerous lies in its fundamental biological structure. Cancer is defined by the uncontrolled division of abnormal, living cells. The hair is not made of living cells; it is composed of a hard protein called keratin.
This keratinized structure forms when cells produced deep inside the hair follicle die and harden as they are pushed upward. Because the hair shaft lacks a nucleus, a blood supply, and dividing cells, it cannot undergo the mutations necessary to form a tumor. Cancer requires active, mitotic cells capable of replicating damaged DNA, a property the hair fiber does not possess. The threat of cancer is confined to the living skin and the active cells within the hair follicle itself.
Cancers That Affect the Hair Follicle and Scalp
While the hair strand is immune, the skin of the scalp is highly susceptible to the same cancers that affect the rest of the body. The scalp is often exposed to ultraviolet (UV) radiation, a primary risk factor for skin cancer development. These cancers typically affect the layers of skin, including the hair follicles.
Basal Cell Carcinoma (BCC) is the most common form, frequently appearing on the sun-exposed scalp. A BCC lesion may manifest as a shiny, pearly bump, a pink growth, or a non-healing sore. This type grows slowly and typically does not spread, but it can cause local tissue damage if left untreated.
Squamous Cell Carcinoma (SCC) is the second most common type and appears as a red, scaly patch, a rough bump, or an open sore that may bleed easily. SCC is more aggressive than BCC and has a higher potential to spread if not treated promptly. People with fair skin, a history of sunburns, or thinning hair are at increased risk for both BCC and SCC.
Melanoma is the least common but most serious form, originating in pigment-producing cells called melanocytes. On the scalp, a melanoma may look like a dark, irregularly shaped mole with uneven borders and multiple colors, or one that changes over time. Scalp melanomas can be aggressive, and early detection is important because they are harder to spot under the hair.
Misconceptions and Non-Cancerous Scalp Conditions
Many common, non-malignant conditions can cause bumps, lumps, or sores on the scalp, leading to concern about cancer. These growths are benign and do not pose a risk of spreading. One of the most common non-cancerous lumps is the pilar cyst, also known as a trichilemmal cyst.
Pilar cysts are firm, smooth, dome-shaped lumps that form beneath the skin, often near the hair root. These cysts are filled with keratin and are harmless, though they can sometimes be mistaken for something more serious. Other benign growths include seborrheic keratoses, which are raised, waxy, scaly growths that can appear brown or black and may resemble melanoma.
Conditions like folliculitis, an inflammation of the hair follicles, can cause small, red, pus-filled bumps that resemble acne. Inflammatory dermatoses like severe psoriasis can cause thick, scaly, and red patches. These conditions, along with benign moles or sebaceous hyperplasia (enlarged oil glands), are distinctly different from cancerous lesions in their cellular makeup and behavior.
The Impact of Cancer Treatments on Hair Growth
The connection between cancer and hair is most widely known through the side effects of certain treatments. Systemic treatments like chemotherapy target and destroy rapidly dividing cells throughout the body, including cancer cells. The cells in the hair matrix, located at the base of the hair follicle, are among the fastest-dividing cells, making them vulnerable to these drugs.
Damage to these hair matrix cells causes the hair shaft to narrow and break off, resulting in hair loss known as anagen effluvium. This loss usually begins within two weeks of starting treatment and can affect hair on the scalp, eyebrows, and other body areas. Radiation therapy also affects hair growth, but its effect is localized only to the treated area, and the loss can sometimes be permanent depending on the dose delivered.