A woman in Connecticut has just lived through a nightmare: the removal of a colossal tumour from her ovary.

It weighed as much as an adult person - 60 kilograms (132 pounds), and came in at almost 90 centimetres (3 feet) in diameter.

The 38-year-old patient sought medical help when she ballooned in weight over just two months, averaging about 4.5 kilograms (10 pounds) a week, starting in November last year.

CT scans revealed a mass in her abdomen, and she was referred to gynecological oncologist Vaagn Andikyan at Danbury Hospital - who was gobsmacked.

"I might expect to see a 25-pound ovarian tumour, but a 132-pound tumour is very rare," he said.

"When I met the patient, she was extremely malnourished because the tumour was sitting on her digestive tract, and she used a wheelchair because of the tumour's weight. I wanted to help her, and I knew that we could at Danbury Hospital."

The medical team had to take special care removing the tumour, partially because it was sitting on a major blood vessel, and partially because the patient wanted to retain as much of her reproductive system as possible.

On February 14 this year, it took the team, which included 12 surgeons, five hours to remove the tumour.

"During the surgery, we removed this gigantic tumour that originated from her left ovary. We removed her left ovary, her left (fallopian) tube, and we removed the affected peritoneal tissue that was adhering to the ovary," Andikyan told CNN.

They also removed the excess skin that the tumour had stretched out across the patient's abdomen, and reconstructed the damaged abdominal wall.

The tumour turned out to be benign - a type of growth categorised as mucinous.

Ovarian mucinous tumours - so-named because they're filled with a mucus-like substance - constitute around 36 percent of all epithelial ovarian tumours. Around 81 percent of them are benign, with 14 percent borderline, and the remaining 5 percent malignant.

They also tend to be very big, but still not normally as massive as 60 kilograms.

"Tumors this big are exceedingly rare in the literature," Andrikyan said. "It may be in the top 10 or 20 tumours of this size removed worldwide."

Large growths like this do show up, though. In 2013, doctors reported a case where they had removed a similar tumour from the abdomen of a 55-year-old woman in India. It came in at 56 kilograms (125 pounds).

The biggest tumour on record was reported in 1994. The 34-year-old patient had a multicystic ovarian mass that hit 137.4 kilograms (303.2 pounds). It had kept her bedridden for two years prior to removal.

Andrikyan's patient went home after two weeks and, three months after the surgery, is recovering well, and has gone back to work as a teacher.

"Luckily, she did not require any additional treatment. She's back to a normal life, she's back to work, and when I saw her in my office, I saw smiles, I saw hope, and I saw a happy woman who is back to her normal life and her family," Andrikyan said.