One of my friends in college, noticed a lump in her neck one day. Up until then, she had not been sick, and showed no signs of any type of illness. She went to the medical center on campus, and they misdiagnosed her, and sent her back to the dorm with a prescription for antibiotics.
She took the antibiotics, and continued going to classes. She went on normally for a month or so until it was time for winter break. When I came back from winter break I learned that she had been diagnosed with neck and head cancer. She had started to feel poorly during the break and she had gone to her doctor, who sent her for tests.
She went downhill very quickly. She wasn't able to return to school because she was going through head and neck cancer treatment, and I lost track of her, but she never recovered from the cancer. It's amazing how quickly the disease caused her health to deteriorate.