Painful and Enlarging Right Breast

A 40-year-old nulliparous woman presents to her primary care physician with a 1-month history of painful fullness of the right breast accompanied by slight redness of the overlying skin and a sensation of warmth. The patient is not taking any drugs and does not smoke. To her knowledge, none of her family members has had breast cancer. She has no history of weight loss, fevers, or chest pain.

On physical examination, the patient has normal vital signs. Cardiovascular and respiratory findings are unremarkable. On breast examination, the right breast is generally tender and appears to be slightly larger and warmer than the left breast. Erythematous, thick, and indurated skin is observed over a questionable underlying mass approximately 5 X 3 cm. The nipple is normal, and no discharge is noted. Several mobile lymph nodes are palpated in the right axilla. The left breast is normal. No palpable masses and no lymph nodes are appreciated in the left axilla.

Mammograms of both breasts are obtained (see Images).

Given the patient's clinical history and mammographic findings, what is your diagnosis?

What is the diagnosis?
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This entity clinically simulates inflammatory condition.