I found this: Satellite tumor nodules in the skin are separate from the primary tumor and macroscopically identifiable. Skin and dermal satellite nodules identified only on microscopic examination and skin involvement without epidermal ulceration or skin edema (clinically peau d’orange) do not qualify as pT4b category (Fig. 4A, ​,B).B). Such tumors should be categorized based on tumor size. Inflammatory carcinoma is categorized only when there are clinical symptoms of erythema and edema in more than one-third of the entire breast skin and not by the pathologic findings of tumor emboli in the dermal lymphatics. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7829577/

Info on the pT4b category https://pubmed.ncbi.nlm.nih.gov/18215492/

What I got, as a lay person, is that the cancer in your skin has a better prognosis if it has not broken the skin. Dito if swelling/redness covers less than 1/3 of the breast. But a doc could interpret and explain.