You are answering a USMLE-style medical question. Question: A 45-year-old woman comes to the physician for the evaluation of a right breast mass that she noticed 3 weeks ago. It has rapidly increased in size during this period. She does not have pain. Vital signs are within normal limits. Examination shows large dense breasts; a 5-cm, nontender, multinodular mass is palpated in the right outer quadrant of the right breast. There are no changes in the skin or nipple. There is no palpable cervical or axillary adenopathy. Mammography shows a smooth polylobulated mass. Biopsy of the mass shows papillary projections of epithelial-lined stroma with hyperplasia and atypia. Which of the following is the most likely diagnosis? Options: A) Phyllodes tumor B) Fibroadenoma C) Fibrocystic disease of the breast D) Invasive lobular carcinoma Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.