A 57-year-old woman who has not seen a physician in more than 20 years, now presents with left breast pain. On examination, the left breast is markedly erythematous, swollen and warm to touch. There is also significant dimpling of the breast (peau d'orange). In addition, the left nipple is completely retracted. Which of the following is the likely diagnosis?

The presentation is that of inflammatory carcinoma of the breast, which typically has an extremely poor prognosis. The name "inflammatory" is a misnomer, as typically no inflammation is present. The underlying carcinoma is usually diffusely infiltrative and typically does not form a discrete palpable mass. In this variant, cancer cells have invaded the skin and suspensory ligaments of the breast, causing dimpling and distoion of the normal breast architecture.