Any early symptoms in retrospect?

No - I never had any 'thing' I can look back at say "I thought 'something' might have been going on.".  I had a routine mammo in late June with no changes/nothing different.  Aug.1,  I found an enlarged (about the size of an almond) node under arm that definately had not been there the night before.  My PA was on vacation so it took me a week to see her.  The 'almond'  had become a 'lime' in that week.  The enlarged node was the first 'sign' - in the 18 days between DX and starting neoadjuvant chemo, I had developed enlargement in breast, peau d'orange and inverted nipple.  Aug 7 I saw my PA and had a new mammo and sono followed by biopsies.  The node was biopsied (and somewhere else in breast that Radiologist wanted to do) immediately.  Had path at 8 the next morning - with want was expected - IBC.

Watch out for that "by definition" thing. IMHO there are too few of us, and still too little data for definitions to be so rigid. At first I was told, it's not IBC because the skin isn't red and "by definition if the skin isn't warm and red it's not ..." .... Later on, a more intelligent, or more up to date oncologist said, it's IBC, "but a different kind."  In any case, it is being treated as IBC.  

My first signs were itching in the breast (I thought it was a reaction to a new bra) - then stinging and discomfort (thought it was a spider bite), then swelling (thought it was mastitis), then white build up behind the nipple. Still, I put off going for a mammo for a few months. Finally when I went, the technician could tell by looking at the breast and touching it that I was in trouble, and did biopsies right away, thank God, because the mammography showed nothing.