A 30-year-old model from East Anglia asserts that her 32OO breasts exceed the sizes of those previously recognized as Britain’s largest, including 34M and 30M cups. Tianna Moon, who shares her journey online, attributes the rapid expansion to gigantomastia, a rare condition causing excessive breast tissue growth.
Rapid Growth After Diagnosis
Moon discovered her condition last year following the use of the weight-loss injection Mounjaro. Her bra size jumped from 38M to 34NN, and within a month, it reached 32OO. She states, “My breasts are much bigger than those claiming the title. I’m running out of alphabet at this point. I am genuine; unlike a lot of other people claiming the title.”
Moon emphasizes that her growth is entirely natural, without cosmetic enhancements or reliance on US sizing. “Many of those who claim to have the biggest breasts involve cosmetic enhancement or rely on US bra sizing alone,” she explains. “My situation is different as my chest growth is entirely natural. I just let my boobs do what they want. Although I do hope they stop at some point. If anybody is bigger than me, I’d love to meet them.”
Early Challenges and Attention
From a young age, Moon’s breasts have been notably large, drawing significant attention. She recalls, “I remember walking home from school as a 13, 14-year-old and it was quite common to have grown men leering at me and honking their horns and stuff.”
Career Shift and Earnings
After a head injury prevented full-time work, Moon launched an adult content career in 2021. She now earns approximately £10,000 monthly from subscribers who appreciate her figure. “I might as well try and reap the benefits of my medical condition rather than the negatives,” she says. “After Covid and furlough I decided I wanted to work for myself and be in charge, manage my own schedule and still make money.”
A subscriber prompted her to get remeasured, leading her to track the ongoing growth despite weight loss in 2024. Researching macromastia led her to gigantomastia.
Medical Confirmation and Daily Struggles
In July 2025, her GP confirmed the diagnosis immediately. “He was point blank like ‘this is gigantomastia’. I got the diagnosis quite early because of the growth not being common with anything else,” Moon shares.
Her breast tissue weighs an estimated four stone, causing back and shoulder pain, exercise difficulties, and challenges finding fitting clothes or bras. She often forgoes bras due to discomfort and availability issues, and sleeping proves challenging from the weight.
