(CBS NEWS) -- A 71-year-old woman from Pennsylvania lost more than 180 pounds in just one day – and how it happened is incredible.

Over the course of 17 years, Mary Clancey’s weight kept creeping up until she was 365 pounds.

“I’d go to the doctors and he would do tests and he’d do tests and everything would be great,” she said.

It wasn’t until she landed in the ER at Lehigh Valley Hospital that doctors discovered she had 140-pound ovarian cyst.

“This is definitely an anomaly,” said Dr. Randolph Wojcik, a plastic surgeon at the Lehigh Valley Health Network. “Initially you can understand where it was missed, when it was a five-pound tumor. It’s a 140-pound tumor, it’s hard to miss in the later stage.”

Surgeons removed the non-malignant tumor, reconstructed her entire abdominal wall and removed another 40 pounds of skin.

“Her just laying on her back flat compromises her breathing… we had to put her on her side and the mass was on another operating table,” Dr. Wojcik said. “The reconstruction was almost like being a tailor.”

Now she needs a tailor!

“Everybody keeps telling me I look great and I look in the mirror and I think I don’t look like myself,” Clancey said.

She’s excited to start a whole new life as half the person she used to be.

Doctors say this case is a good example of why it’s important to always get a second opinion.