Hi 6ftred
Mucinous carcinoma's tend to be less aggressive than non-mucinous carcinoma's. So that is potentially good news for you (although it probably still means chemo and radiotherapy).
You will need to know more about the cancer's pathology and markers which will happen when they take the lump and process it in the pathology lab (eg is it hormone positive or negative, is it HER positive or negative, is it ductal or lobular etc) before you can work out likely prognosis.
I had a mucinous carcinoma which initially indicated a good prognosis. However, the tumour had a different pathology that is not normally found with mucinous carcinoma's so it was a bit strange. Anyhow, my cancer had spread to my bone - aligning with the more agressive pathology and not the mucinous pathology! Unfortunately, medically I always seem to be an anomaly!
I hope your lumpectomy goes well and the pathology shows a less agressive tumour as indicated thus far.
Cheers
Lisa XXX
