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The cancer that contributed to the death of ESPN college football reporter Ed Aschoff can be notoriously fast-growing and difficult to detect until it has reached an advanced stage.

Aschoff, who died in December at 34, had stage 4 non-Hodgkin lymphoma, his fiancée, Katy Berteau, shared on Twitter on Wednesday.

"After his passing, the hospital received the final results from his lung biopsy," Berteau wrote. "Unbeknownst to us, Edward had stage 4, non-Hodgkin’s lymphoma in his lungs. This is an aggressive type of cancer that is usually undetectable until it is very advanced."

(2/9) After his passing, the hospital received the final results from his lung biopsy. Unbeknownst to us, Edward had stage 4, non-Hodgkin’s lymphoma in his lungs. This is an aggressive type of cancer that is usually undetectable until it is very advanced. pic.twitter.com/kuPHwrAXuz — Edward Aschoff (@AschoffESPN) January 16, 2020

Young people in their 30s can develop aggressive non-Hodgkin lymphoma in a relatively short period of time, said Dr. Brian Hill, a hematologist and director of the Lymphoid Malignancies Program at the Cleveland Clinic in Ohio.

"Some previously healthy people can start to develop symptoms over a period of weeks," said Hill, who was not involved with Aschoff's case.

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Non-Hodgkin lymphoma is a type of immune system cancer that starts in white blood cells called lymphocytes, according to the American Cancer Society. Broadly speaking, the cancer can be grouped into two major categories: slow-moving and aggressive, Hill said.

The cancer can cause growths in a person's lymph nodes, and its location in the body can affect how easy it is to detect. Imaging can reveal the growths, and a biopsy is needed to make the diagnosis.

Growths in the lymph nodes in a person's chest cavity, for example, can become quite large in a relatively short period of time before they're detected, Hill said. Symptoms of the cancer growing in a person's chest cavity can be vague, including a cough or some swelling in the neck, which a young person may brush off as a minor problem, he added.

But a large growth in the chest can cause more serious problems, too. "If a mass presses on a person's airways, that obstruction can prevent germs from exiting the airways," Hill said This could lead to pneumonia.

Hill said that major red flags doctors consider for a diagnosis of non-Hodgkin lymphoma include drenching night sweats, unintentional weight loss, severe fatigue and swollen lymph nodes.

Berteau tweeted in December that Aschoff had pneumonia and was being treated for a presumed diagnosis of HLH, or hemophagocytic lymphohistiocytosis, which is an immune system disease.

"Both pneumonia and non-Hodgkins lymphoma can trigger HLH in the body, and that is seemingly what happened with Edward. All of this combined is what led to his very rapid decline those last few days, and ultimately his passing," she tweeted on Wednesday.

"HLH is a rare event, but it's much more common in patients with non-Hodgkin lymphoma," Hill said.

Hill added that generally, young healthy patients diagnosed with aggressive non-Hodgkin lymphoma can be treated effectively with chemotherapy.

But an event like HLH could explain Aschoff's tragic death, Hill said.

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