Five years ago, when actor Chadwick Boseman died at age 43 from colon cancer, it was a genuine shock. Last summer, when Catherine, Princess of Wales, was diagnosed with cancer at age 42, it was tragic, but it landed a bit differently. At that point, it was clear her diagnosis was part of a clear narrative: More and more relatively young adults are developing cancer.

But now, a more complicated story is emerging.

According to a new study published in JAMA Internal Medicine, some of the rise in early-onset cancer is a diagnostic mirage: Doctors are finding cases that would never have led to serious illness anyway. Younger adults — those under 50 — are indeed being diagnosed with cancer at nearly twice the rate they had been in 1990: 60 cases per 100,000 people, up from 30. But the number of metastatic cases, those that are more likely to be aggressive and/or were detected late, has not increased at nearly the same speed. The death rate for the eight cancers covered in the study has remained flat over the last 35 years.

“Overall, the rise in early-onset cancer appears to be less an epidemic of disease and more an epidemic of diagnosis,” the authors — researchers from Harvard, Brigham Women’s Hospital in Boston, and the University of Texas-Austin — write in their paper’s conclusion.

This surprised me. I’m a bit of a hypochondriac, and I’m an adult under 50, and so when I read a headline about the uptick of cancer among my own generation, I certainly think, Oh no, more young adults are getting sick and dying from cancer.

But there are ways to double-check that assumption — which is exactly what this new paper tries to do.

The authors decided to look deeper into the overall rising rate of cancer incidence among middle-aged adults and focus specifically on rates of metastatic cancer and death rates, metrics that correlate with more serious illness. And the........

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