BOYLE HEIGHTS (CBSLA) – It looked like a beer belly, but it was actually far more ominous.

Hector Hernandez of Downey is a new man these days, but just four months ago, he said his stomach was abnormally protruding.

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For years, he had been getting bigger around the waist. But something didn’t add up.

As Hernandez’s belly was growing bigger, his legs and arms were getting thinner.

“My arms were way smaller than they are now. I used to have have hanging skin,” he said.

A CT scan in June revealed a shocker: Hernandez was diagnosed with a tumor called retroperitoneal liposarcoma.

“They’re the largest tumors, the largest cancers we know about in the human body,” Dr. William Tseng said.

Tseng is a surgical oncologist at USC’s Keck School of Medicine.

“These tumors start at the back of the abdomen. They grow over time and they tend to push organs to the side,” he said.

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Hernandez underwent surgery in July so that doctors could tackle the enemy growing inside him.

“These tumors are typically about maybe 20 to 30 pounds in size. His was 70 pounds,” Tseng said.

Hernandez had been carrying more than 70 pounds of cancer and had no idea.

Tseng said that’s not unusual with this type of abdominal tumor, and there’s usually not pain associated with it.

“The patient’s body actually kind of adapts to the presence of this slow-growing big tumor,” he said.

When Hernandez entered the hospital, he weighed more than 300 pounds. After six hours surgery and a week of recovery, he had lost more than 100 pounds.

“Despite it’s size, the tumor has a low chance of spreading – which means there’s no need for chemo or radiation. But because the disease could come back, doctors will continue to monitor Hernandez.

For right now, there’s no evidence of disease or the tumor.

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Tseng said medical professionals have no idea what causes these tumors, but stresses they are very rare. However, any new swelling around the middle should be checked out to eliminate the potential for a serious medical condition.