Woman with Gigantomastia Claims Britain's Biggest Breasts
Tianna Moon, a 30-year-old woman from East Anglia, says she has the largest natural breasts in Britain, measuring 32OO. Her breasts have grown two cup sizes in the past year due to a rare condition called gigantomastia, a severe form of macromastia that causes rapid and excessive breast tissue growth.
Tianna first noticed abnormal breast growth when she was just 13 years old. She recalls men leering at her and honking horns as she walked home from school. 'It's become so normal to me, I don't even notice it anymore,' she says. 'When I go out in public I try to make them smaller than they are and strap them up – I get stares and double takes.' Now, she says, 'If anybody is bigger than me, I'd love to meet them.'
Diagnosis and Challenges
Last year, Tianna finally learned why her breasts were so large. She was diagnosed with gigantomastia after starting the weight-loss drug Mounjaro in May 2024. While her body slimmed down, losing three stone over a year, her breasts grew from an L cup to an M cup. Puzzled by this odd growth, she searched online medical discussion groups and discovered gigantomastia. A visit to her GP in July 2025 confirmed the diagnosis.
Tianna faces numerous challenges due to her condition. 'The side effects are having numb arms quite a lot and having quite severe indentations on my shoulders. Things like running and jumping can be risky, since they often smack me in the face,' she explains. She also has light scarring under her breasts from bra straps rubbing and ripping the skin. Lying on her back restricts airflow. Finding bras is nearly impossible, as UK manufacturers stop at an M cup. 'Even before I maxed out the sizes, my breasts would often break the wires clean in half,' she says.
Turning a Condition into a Career
Despite the difficulties, Tianna has turned her condition into an advantage. She joined OnlyFans in 2021 after a head injury left her unable to work, and now earns £10,000 monthly from admirers. 'I might as well try and reap the benefits of my medical condition rather than the negatives,' she explains. Interestingly, a subscriber noticed her breasts were growing and suggested she get remeasured, which led to her monitoring the growth.
However, not all attention is positive. 'People are telling me it's disgusting I'm not having a reduction and that I'm basically begging for attention,' she says. Tianna has considered breast reduction surgery but fears the tissue may grow back. She underwent a gastric sleeve in November 2025 to protect her back and has been referred for physiotherapy.
Similar Cases
Another woman with gigantomastia, Summer Robert, 25, also shares her story. With a 30N or 28 O-cup size, she carries about 25kg of weight on her chest daily. Refused a breast reduction due to her BMI, Summer turned to OnlyFans and wears a doctor-prescribed corset to manage pain. 'I swim a lot because I'm weightless so it's a relief, but then I get out the pool and it feels horrific,' she says. Both women have turned their condition into a positive, embracing their bodies and finding support online.
Only about 300 cases of gigantomastia have been recorded worldwide, making Tianna one of a rare few. She hopes her breasts will eventually stop growing, but for now, she says, 'I just let my boobs do what they want.'
