Written or medically reviewed by a board-certified physician. See About.com's Medical Review Policy.

Updated January 05, 2015.

Cancer is a disease of aging.  That’s because it takes years, often decades, before enough damage occurs to the DNA (the genetic material) within cells until one cell is finally transformed into a malignant monster, a cell that never dies, a cell that divides into a ball of identical cells (a tumor) which destroys neighboring tissues, a cell which is capable of traveling and invading and destroying other body parts (cancer metastasis).

  Thus it takes decades of inhaling cigarette smoke to trigger lung cancer, and decades before the teenager who suffers repeated sunburns sees a skin cancer on his or her chest.  And all those cancers not linked to our behaviors also require years and years to accumulate the multiple “spontaneous mutations” that create a malignant cell.

We screen for common cancers based on this view of cancer as a disease of middle and older age.  Thus, you should first undergo colonoscopy to screen for pre-cancerous colorectal polyps at age fifty.  And women should have their first mammogram at age forty.  For men, the first “finger wave” to feel for early prostate cancer and, if recommended, a blood PSA test, happens at age fifty.  (These guidelines are for the majority of people with no known cancer-specific risk factors.)

Yep.  Cancer is a disease of aging.

Except for the more than 70,000 young Americans between the ages of 15 and 39 who are diagnosed with cancer each and every year.  Seventy thousand.

That’s right.  For this group whom we refer to as “adolescents and young adults” (AYA), cancer is the leading cause of disease-related death.  As this year draws to an end, there are nearly 1.7 million adolescents and young adults currently battling a malignancy while decking the halls.

For those of us (well) past this period in our lives, we recall what an exciting time of life this was:  new educational and career opportunities; new relationships; marriage; babies.  It is for many a truly wonderful time.  Now imagine hearing in the midst of this wonderful time, “You have cancer.”  And what makes hearing that diagnosis worse for many young people is that relative to typical, older cancer patients, they receive their diagnosis much later after their cancer was detectable.  That is, a delayed diagnosis is the norm for AYA cancer patients.  And a later diagnosis may mean a more advanced cancer, the need for more aggressive treatment, and, potentially, a worse prognosis (chance of survival).

Why is cancer diagnosed later in younger people?  There are a couple of key reasons.  First, few adolescents and young adults truly consider cancer when they become chronically fatigued, when they experience night sweats or worsening constipation, or when they suffer other vague (what we call “non-specific”) feelings.  They chalk it up to a cold, the flu, working too hard, partying too hard.  And young women don’t routinely perform breast exams nor young men testicular exams.  Nor do AYA routinely look for new, small, dark skin spots when standing in front of the mirror.  Nope.  Young people neither consider cancer when they “just don’t feel well” nor regularly examine themselves for potential cancers. Why should they?  After all, cancer is a disease of aging.

And young cancer patients have a partner in the delay in diagnosis:  clinicians.  Physicians and nurses are trained to immediately consider cancer in patients who are fifty or older.  And we have heightened awareness of pediatric cancers, even though AYA cancers are many times more common than childhood malignancies.  But healthcare providers routinely fail to consider a malignancy when first evaluating a young person, especially one with non-specific complaints such as “tiredness for months.”  And unfortunately, many of the most common AYA cancers, such as lymphoma and leukemia, produce such non-specific symptoms.  Other AYA malignancies, such as breast, thyroid, and testicular cancer, do present with a growing mass, but since young people don’t often perform self exams or undergo regular physician examinations, the tumors often attain a large size and the cancer stage may be more advanced when finally diagnosed.  And for those malignancies that tend to hide even in the older population, such as colorectal and ovarian cancer, the delay in diagnosis caused by both the young patient and the clinician again means a delay in treatment and, often,  more advanced disease.

So what’s the take-home message?  That depends on your age.  If you’re a parent of an adolescent or young adult, don’t stop parenting:  regularly ask your child how they’re feeling, and don’t simply accept their reassurances that the weeks of fatigue or sweats or constipation or low-grade fevers are simply the result of working (or playing) harder than usual.  You’re a parent, so you’re entitled to be pushy.  Get them to the doctor.  And if you’re an adolescent or young adult, don’t blow off general, non-specific symptoms, particularly if they don’t go away within a couple of weeks.  And take a moment every month to look at your skin for new spots or changes and to correctly perform a breast or testicular exam. 

Smart young people own their health and protect themselves.  And fortunately, there is growing awareness among young people and clinicians about AYA cancers, and amazing organizations (like Stupid Cancer®) to help AYA cancer patients through the challenges.