A 51-year-old woman has noticed an area of swelling with tenderness in her right breast that has worsened over the past 2 months. On physical examination, the 7-cm area of erythematous skin is tender with a rough, firm surface resembling an orange peel. There is swelling of the right breast, nipple retraction, and right axillary non-tender lymphadenopathy. Excisional biopsy of skin and breast is most likely to show which of the following lesions?

The gross appearance of the skin is consistent with the invasion of dermal lymphatics by carcinoma - the so-called inflammatory carcinoma, which is not a histologic type of breast cancer, but a descriptive phrase based upon the gross appearance (peaud'orange) resembling an inflammatory process. Nipple retraction and non-tender axillary lymphadenopathy also suggest invasive ductal carcinoma. Atypical ductal hyperplasia may increase the risk of carcinoma, but it is not capable of invasion and does not produce visible surface skin changes. Acute mastitis may produce pain and swelling, but it is more likely to occur in association with breastfeeding, and as an inflammatory process would be more likely to produce painful lymphadenopathy. Fat necrosis on palpation can mimic that of carcinoma, but the skin is not involved. Sclerosing adenosis is a feature of benign fibrocystic changes producing breast lumps, but it has no skin involvement.