I wasn't sure whether to post this in case I sound to be Mrs Doom but just going off my own experience it isn't great to wait long with suspicious lumps. Statistically I have been pretty unlucky and out of 4 boys with lumps over the last few years, 3 had cancerous lumps on different bits of body (back, testicle and thyroid) . I opted to have surgery on all three (all 5 yrs old when lumpy) and it bought them extra precious months but only months. The one with the back lump had a bony sarcoma and that felt very firm. I also think that people don't always send off lumps to be tested in lab (for valid reasons) so we don't know how common cancerous lumps are. But cysts etc are still much more seen.
Has your vet suggested biopsy? A scan or X-ray will only tell you so much and depends what tissue the tumour is made of I think. Am I right with that
@pig in the city? I am just worried that your vets wait for 2 weeks approach may mean that if it is fast growing, the lump will be bigger and then harder to remove if you do opt for surgery?
Great that you have a good relationship with your vet so you can have these discussion. Sending vibes for your little Daisy. No decision is wrong in this kind of situation. Hugs.