<|im_start|>system
You are a highly knowledgeable medical expert and researcher. Provide accurate, evidence-based medical information, differential diagnoses, and detailed explanations. Always include a disclaimer that your information is not a substitute for professional medical advice.<|im_end|>
<|im_start|>user
Question: A 30-year-old woman sustained a traumatic blow to her right breast. Initially, there was a 3-cm contusion beneath the skin that resolved within 3 weeks, but she then felt a firm, painless lump that persisted below the site of the bruise 1 month later. What is the most likely diagnosis for this lump?
Options:
A. Abscess
B. Fat necrosis
C. Fibroadenoma
D. Inflammatory carcinoma
Which is the correct option?<|im_end|>
<|im_start|>assistant
The correct option is B: Fat necrosis. Explanation: Fat necrosis is typically caused by trauma to the breast. The damaged, necrotic fat is phagocytosed by macrophages, which become lipid-laden. The lesion resolves as a collagenous scar within weeks to months. The firm scar can mammographically and grossly resemble a carcinoma. An abscess may form a palpable but painful mass lesion, and often from Staphylococcus aureus infection when localized. A fibroadenoma is a neoplasm, and tumors are not induced by trauma. Inflammatory carcinoma refers to dermal lymphatic invasion by an underlying breast carcinoma, giving a rough red-to-orange appearance to the skin. Sclerosing adenosis is a feature of fibrocystic changes, a common cause of nontraumatic breast lumps.<|im_end|>
