A medical team removed the tumour in a five-hour procedure at Danbury Hospital.
A 132-pound (around 60 kg) ovarian tumour, measuring almost three feet, was removed from a 38-year-old woman, from Connecticut in the United States, this year, said doctors involved in the case.
The patient, who wished to remain anonymous, reported that the tumour began growing at a rate of about 10 pounds per week in November 2017.
A medical team, including 12 surgeons, removed it in a five-hour procedure on February 14 at Danbury Hospital in Connecticut, said Vaagn Andikyan, a gynaecologic oncologist for Western Connecticut Health Network and a lead surgeon on the case.
They removed her left ovary, where it originated, her left (fallopian) tube, and affected peritoneal tissue adhering to the ovary, CNN reported.
Three months since the surgery, the patient is recovering well and has returned to work as a teacher.
"Ovarian mucinous tumours tend to be big," Dr Andikyan said. "But tumours this big are exceedingly rare in the literature. It may be in the top 10 or 20 tumours of this size removed worldwide."
The tumour was though benign, was compressing nearby blood vessels and was therefore a threat to the patient's life, CNN quoted the doctor as saying. "She was at very high risk of developing blood clots."
On first examination, the woman appeared malnourished with a weight of 350 pounds and extensive tumour that was about 100 cm large.
"The good part about this story is, we were able to save her reproductive organs," the doctor told CNN.