Hi Mairi,

Generally I'd ask the client what observations the diagnosis is based upon, because that may tell us more than the label itself. And of course, her own sensations and how her breast has changed.
A tumor in situ may be a relic from an earlier process, but the signs you describe sound like an active process. Growing could be interpreted as swelling, as cell hypertrophy or as cell multiplication. Together with signs of inflammation (swelling, warmth, redness) it would rather be due to decomposition of (tumor) tissue.
Inflammation is seen throughout regeneration phase, lesser after the healing peak. I'd expect puckering to occur where there is inflammation.
The information is not specific enough to say anything valid, these are only general assumptions.