The 10 deadliest cancers, and why there's no cure

Microscope image of an adenocarcinoma in the pancreas. Cancer cells can be seen in dark pink and purple concentrated in a blob in the center of the image. Normal cells can be seen in purple dotted about around it with white gaps in the image where no cells are present. .

There's no doubt that cancer is deadly: In the United States, the disease is the second-most-common cause of death, after heart disease, according to the Centers for Disease Control and Prevention (CDC). Even when diagnosed and treated early, cancer has the potential to kill.

According to the World Health Organization, the three cancers that killed the most people worldwide in 2020 were lung cancer (1.8 million deaths), colorectal cancer (916,000 deaths) and liver cancer (830,000 deaths). Prostate cancer and breast cancer, meanwhile, are among the most common types of cancer.