Top (chest) Surgery on Teenagers
The best and most comprehensive document on all aspects of transgender and non-binary physical and mental health is the World Professional Association for Transgender Health (WPATH)'s Standards of Care. They collect data from peer-reviewed studies, white papers (individual organizations that put out recommendations), and medical case studies. The current version is #8 and can be found online here: https://www.tandfonline.com/doi/pdf/10.1080/26895269.2022.2100644
The section that applies to adolescents and teenagers is section 6, starting on page 45 of the document.
To summarize the WPATH guidelines, teenagers can be candidates for top surgery depending on their age, health history, mental health, and their ability to understand informed consent about the procedure. They recommend that top surgery can be done at age 16+, although individual surgeons have done top surgeries on teens at age 14 and not followed the standards of care.
WPATH guidelines state that a multidisciplinary team be working with the teen, including gender-affirming therapy, well-informed primary care doctors and surgeons, and parental/guardian support.
The teenager usually has to be diagnosed with gender incongruence or gender dysphoria for a period of 12+ months or more, depending on the country (ICD-11 diagnostic code). The teenager also has to demonstrably show that they understand the risks, potential outcomes, and the effects on breast/chest feeding in the future. They have to show that they are cognitively developed enough to understand that gender expression can change over time, that they have had timne to self-reflect on if this decision is right for them, and that they can think carefully about future implications of having the top surgery.
For transmasculine youth, they found that having chest dysphoria is associated with higher rates of anxiety, depression, and mental distress, even when the teenager can bind their chest (but especially if their chest is too big to bind effectively). HRT is NOT required (or should not be required) to have top surgery, as testosterone does not alleviate chest dysphoria.
So far, studies have shown that transmasculine teenagers who have top surgery have good surgical outcomes, satisfaction with the results, and a very very very low incidence rate of regret.
Here are some of the studies referenced:
https://www.tandfonline.com/doi/full/10.1080/15532739.2017.1349706
WPATH Standards of Care v.8 https://www.tandfonline.com/doi/pdf/10.1080/26895269.2022.2100644