@kezmusc one of the eleventy thousand forms you probably signed pre-surgery (or at some other stage during the shitfight) would have been a permission to retain a sample of your tumour/s that can be used for scientific and research purposes. I asked the same question not long ago--what happened to those bits of the tits? The answer was 'It depends.'
Tissue banks are supposed to be de-identified. All the relevant information is kept, apart from your name. That, in theory, should mean I can't request a sample I donated 13 years ago be retested to give me more information that might inform future treatment decisions. This, from what I was told, only seems to apply to donated tissue samples (wee scrapes on a slide, usually, not a wrinkled lemon floating in formaldehyde) but it appears some services do keep larger identified samples, but I've never figured out who/how/where. Being a commoner with no health insurance and a not-so-terribly-remarkable cancer, I'm assuming mine went into the communal mince. Mxx