Orange-like rash on breast -awaiting diagnosis

for about 7 days know I have had a rash only about 1 inch in diameter on my breast. It is hot and itches. It looks like shingles and hives combined. Sort of like an orange peel in texture but red like hives.
My doctor is aware of inflammatory breast cancer but thinks that despite the texture doubts it is IBC. He thinks it is a skin irritation and has given me antibiotic pills and a cortisone cream to apply. He said to come back in 4 days if the rash does not improve significantly.
My breasts feel denser than usual(I have always had lumpy feeling breasts and the density change might me due to hormonal changes) I had a sonogram of my breasts immediatly but they saw nothing. However, I am aware that IBC diagnosis often occurs where no tumour is visible in mamograms/sonograms nor are palpable.
I have a few questions about IBC diagnosis. Any advice would be much appreciated.
1)With IBC diagnosis, do the skin changes normally to occur to the whole breast or does the cancer form in small patches as well?
2)When I am feeling cooler, the redness subsides a bit and when I am hotter (even though I protect the rash from any sun exposure) it gets more red. With IBC, can the rash change in colour or is this a sign that it is not IBC?
3)Is it possible that antibiotic/cortisone treatment can delay diagnosis of IBC because the treatments can alter the appearance of the skin temporarily?
My doctor said that in 4 days if there is no significant change, he will refer me to a breast specialist and order a mammogram right away.
I plan to be very aggressive about this because I grasp how fast IBC can progress and I would very much appreciate feedback from people who are knowledgeable in the three areas I had questions about (changes in the rash, size of rash and antibiotic treatment).
Thank you very much, blessings, Idas Levato Toronto, Canada.

IBC is a bit beyond my knowledge, but I`d make these points.
Inflammation of any sort can make the surrounding tissue feel swollen and lumpy. to 1), I am pretty sure IBC can occur as a small patch, and could fit your description, but so can other things. to 3), If it responds to antibiotics or reduces of its own accord then it almost certainly isn`t cancer.
The doctor`s response sounds sensible.