Some legal and clinical references about the possibility for minors to have their breasts removed:
In its press release dated February 25, 2022, the Right Honourable Academy of Medicine provides information on the medicalization of gender dysphoria in minors.
Extract:
"While in France the use of hormone blockers or hormones of the opposite sex is possible with parental authorization without age conditions, the utmost reserve is required in this use, given side effects such as the impact on growth, bone fragility, the risk of sterility, emotional and intellectual consequences and, for girls, symptoms reminiscent of the menopause.
As for surgical treatments, in particular mastectomies authorized in France from the age of 14, and those involving the external genitalia (vulva, penis), their irreversible nature must be emphasized."
The testimony in the daily Le Parisien of a young woman who detransitioned at 19, reveals that she underwent a mastectomy at 16:
Extract:
"The summer before his senior year, he had his breasts removed under general anaesthetic. "I was obsessed with the idea of being able to take the sports test at the bac breathing" (i.e. without a compressive binder on the chest), he recalls. After the operation, the high-school student was now 16, wearing an osthetic corset, taking painkilling tablets galore, and suddenly questions were assailing him. "There was a strange voice inside me. Something asking me: Are you destroying your life? Are you destroying your body?"
In an article published by Médiapart, the team of nurses at a Parisian service that assists minors in transition talks clearly about these surgeries:
Extracts:
"As for surgeries, here too the three teams are unanimous: "Only torsoplasty is possible before the age of 18.""
(...)
"Treatments that include an element of irreversibility are therefore best started from the age of 16",
Finally, Anne Barghiacci (child psychiatrist) and Laëtitia Martineri (endocrinologist) report on the medicalization of trans-identified young people at the Cycle Droit et Bioéthique: identité, sexe et genre conference.
Excerpt:
(At 24:30 on the video): "Mastectomy is the only surgery that is authorized before the age of 18 with parental consent."
They go on to say that it's not quite an authorization, but that "there's no law".