A 58-year-old woman has a screening mammography and is found to have a 4-cm circumscribed mass, without calcifications, in her left breast. An excisional biopsy shows solid nests and sheets of highly pleomorphic cells, with many mitotic figures, surrounded by a dense infiltrate of lymphocytes. Which of the following is the most likely diagnosis?
- Invasive ductal carcinoma
- Invasive lobular carcinoma
- Medullary carcinoma
- Paget disease
- Phyllodes tumor