Squamous cell carcinoma (SCC) is a common type of skin cancer that can affect people of any age, but it is most often diagnosed in older adults. The risk of developing SCC increases with age due to cumulative sun exposure over one’s lifetime. SCC rarely affects children and adolescents, but can become more prevalent starting around age 50. The average age at diagnosis of SCC is the mid-60s.
What is squamous cell carcinoma?
Squamous cell carcinoma (SCC) is a type of skin cancer that begins in the squamous cells, which are flat cells found in the outer layer of skin (epidermis). SCCs often develop on sun-exposed areas of the body such as the face, ears, neck, lips, and backs of the hands. Less common sites include the genitals, inside the mouth, and on skin with long-term inflammation. SCC tumors tend to grow slowly and usually do not spread to other parts of the body, although they can be disfiguring if allowed to grow.
What causes SCC?
The most significant risk factor for developing SCC is cumulative ultraviolet (UV) light exposure from the sun or indoor tanning over one’s lifetime. The risk increases with more total sun exposure and with episodes of severe sunburns. People with fair skin, light hair and eye color have less skin pigment (melanin) to protect against UV radiation and are more susceptible to SCC. Using tanning beds before age 30 increases SCC risk by 75%. UV damage can cause genetic mutations in skin cells that lead to uncontrolled growth and tumor formation.
Other SCC risk factors include:
- Older age (50s and up)
- Male sex
- Weakened immune system
- HPV infection
- Chemical exposure (arsenic, coal tar, paraffin)
- Ionizing radiation
- Chronic inflammatory skin conditions
- Scars from burns, infections, etc.
- Certain rare genetic syndromes (e.g. xeroderma pigmentosum, albinism)
Incidence of SCC by age
The incidence of SCC, meaning the number of new cases diagnosed per year, rises steadily with age. Very few cases occur in children and younger adults. Below is a breakdown of SCC incidence rates by age group:
- Ages 0-29: 1.6 cases per 100,000 persons
- Ages 30-39: 11.1 cases per 100,000 persons
- Ages 40-49: 58.1 cases per 100,000 persons
- Ages 50-59: 204.4 cases per 100,000 persons
- Ages 60-69: 394.7 cases per 100,000 persons
- Ages 70+: 651.9 cases per 100,000 persons
These statistics from the American Cancer Society demonstrate the strong age-associated increase in new SCC cases. The risk rises exponentially starting around age 50. Although less common, SCC can occasionally affect younger adults, especially those who tan, use tanning beds, have fair skin, or are immunocompromised.
Why SCC rates increase with age
There are several reasons why SCC incidence climbs steadily with advancing age:
- Cumulative sun exposure – The risk of SCC is closely linked to lifetime UV radiation exposure. Older people have had more years of sun exposure.
- Increasingly fragile skin – Skin loses elasticity, becomes thinner, and repairs damage less effectively as we age, making it more vulnerable to cancer-causing UV damage.
- Weakened immunity – Immune function declines with age, impairing the body’s ability to detect and destroy precancerous cells before they form tumors.
- Higher mutation risk – Advancing age increases the number of genetic mutations accumulated over time, some of which can trigger abnormal cell growth.
- Existing precancerous areas – Older skin already contains more actinic keratoses and precancerous lesions that can progress to SCC.
Age distribution of SCC patients
Many studies have assessed the age distribution of patients at the time they are diagnosed with SCC. The results consistently show that only a small fraction of cases occur before age 40, with the majority of patients being older adults over 60 years old.
For example, an Australian study published in 2013 tracked SCC incidence by age group for all patients diagnosed over a 20-year period. The results were as follows:
| Age Group | Percent of Total SCC Cases |
|---|---|
| 0-39 years old | 6% |
| 40-59 years old | 22% |
| 60-79 years old | 44% |
| 80+ years old | 28% |
This real-world data shows that 72% of patients diagnosed with SCC were over age 60, while only 6% were under 40. Other studies have produced very similar results regarding the age distribution at diagnosis.
Why most SCC cases occur in older adults
There are several reasons why the majority of squamous cell carcinoma cases are found in older adults:
- Older people have had many more years of sun exposure, increasing their skin cancer risk.
- Immune function weakens with age, allowing cancers to grow rather than be eliminated.
- Advancing age leads to increased genetic mutations and DNA damage in skin cells.
- Elderly skin contains more precancerous lesions that can progress to SCC tumors.
- Skin cancer screening is less frequent in younger people compared to older adults.
- Younger people may ignore early SCC warning signs before diagnosis.
Therefore, while possible at any age, the development of most SCC tumors requires decades of cumulative sun damage, genetic mutations, and loss of tumor immunity that occurs during aging.
Average age at SCC diagnosis
Population-level studies have calculated the average age at which patients are first diagnosed with squamous cell carcinoma of the skin. This represents the typical age when SCC detection and treatment occurs based on all reported cases.
In the United States, the average age at diagnosis for SCC is around 66 years old. The American Cancer Society provides a detailed breakdown by age and sex:
- Males: Average age of 69 years old at diagnosis
- Females: Average age of 63 years old at diagnosis
- Overall: Average age of 66 years old at diagnosis
This data shows SCC tends to be detected slightly earlier in women compared to men. But overall, most cases are diagnosed in a person’s 60s. Other studies have produced similar results regarding the mean or median age of initial SCC diagnosis, which falls within the 60s decade for both men and women.
Why is the average age of diagnosis in the 60s?
There are several reasons squamous cell skin cancers are typically detected in a person’s 60s:
- Most people accumulate enough sun damage by their 60s for SCC to develop.
- Skin aging and fragility increase significantly around age 60.
- Immune function starts to notably decline in a person’s 60s.
- More doctors screen for skin cancer in older adults.
- Individuals are more alert to changes on their skin around age 60.
- Existing precancerous lesions are likely to progress to SCC in a person’s 60s after many years.
In summary, the intersection of sun exposure duration, skin changes, immune changes, and screening practices makes the 60s the most common decade for SCC diagnosis.
Risk of SCC by age group
While people of any age can develop squamous cell carcinoma, the risk increases substantially with age. Population statistics have been used to calculate the risk of being diagnosed with SCC based on age group. The results highlight the dramatic rise in risk that occurs with aging.
According to data from the CDC, the odds of developing SCC by age group are:
- Ages 0-29: 1 in 2,000 risk
- Ages 30-39: 1 in 600 risk
- Ages 40-49: 1 in 150 risk
- Ages 50-59: 1 in 50 risk
- Ages 60-69: 1 in 15 risk
- Ages 70+: 1 in 8 risk
These numbers illustrate how the risk climbs exponentially with each advancing decade of life due to accumulating sun exposure, precancerous skin changes, reduced immunity, and other age-related factors.
Why SCC risk increases with age
There are several reasons why growing older substantially increases a person’s risk of developing squamous cell carcinoma of the skin:
- Each decade of life adds more accumulated sun/UV exposure that damages skin cells.
- Advancing age leads to more mutations and precancerous areas in skin.
- Immune function progressively declines with aging, allowing tumors to grow.
- Elderly skin is more fragile and less able to repair UV damage.
- Skin cancer screening is performed more often in older groups.
While still possible in one’s 20s or 30s, the risk of SCC is extremely low. But with each decade, the chances of developing SCC tumors climbs exponentially due to various aging factors.
Risk factors for SCC in young people
Although relatively rare, squamous cell carcinoma can occasionally affect younger adults and even teenagers. However, there are often additional risk factors present beyond just sun exposure.
Risk factors that can contribute to developing SCC at a younger age include:
- Severe lifetime sunburns
- History of tanning bed use
- Immune suppression medications
- HPV infection
- Genetic skin cancer syndromes (xeroderma pigmentosum, albinism)
- Ionizing radiation exposure
- Chemical exposure (arsenic, coal tar)
- Chronic inflammatory skin conditions
- Burn scars or chronic wounds
For example, a 20 year old who frequently uses tanning beds and has a medical condition causing immune deficiency would be at higher risk for early SCC. But in general, these additional factors would be present in younger SCC patients rather than just general sun exposure over time.
Examples of young people at risk
Some examples of younger demographics with elevated SCC risk include:
- Organ transplant recipients – Anti-rejection medications suppress immunity, increasing skin cancer risk.
- HIV patients – HIV infection impairs immune function, allowing tumor cells to grow.
- HPV-positive individuals – High-risk HPV strains can trigger growth of SCC in the anogenital region and mouth.
- Tanning bed enthusiasts – Early tanning bed use significantly boosts skin cancer risk.
- Xeroderma pigmentosum patients – This genetic disorder impairs ability to repair UV damage, leading to extremely high SCC risk, often in childhood.
Therefore, while possible in the young, additional factors beyond just lifetime sun exposure usually contribute to early SCC development.
Preventing SCC at a young age
While squamous cell carcinoma predominantly affects the elderly, in rare cases it can occur in younger people. To minimize SCC risk at a young age:
- Avoid excessive sun exposure and tanning beds.
- Use broad spectrum sunscreen daily.
- Get any changing moles or sores evaluated promptly.
- Don’t smoke or chew tobacco.
- Consider genetic testing if family members had early skin cancers.
- Discuss any concerning lesions or risk factors with your dermatologist.
catching any suspicious growths early, protecting your skin, and avoiding additional risk factors can help reduce odds of developing SCC at a young age when it’s less common.
Conclusion
In summary, squamous cell carcinoma predominantly occurs in older adults, with an average age at diagnosis in the 60s. The risk increases exponentially with advancing age due to cumulative sun damage, precancerous skin changes, waning immunity, and other aging factors. While much less common in the young, certain risk factors like sun overexposure can potentially lead to earlier SCC development. Reducing UV exposure, avoiding tanning, performing monthly skin self-checks, and promptly treating any suspicious lesions are important at any age to help minimize risk of squamous cell skin cancer.
