Palpable Breast Lump After a "Normal" Screening Mammogram
47-year-old woman presents because she felt a new lump in her right breast 3 weeks after an outside screening mammogram. The report describes heterogeneously dense tissue and assigns BI-RADS 1, with no prior comparison. She has no personal history of breast cancer; her mother was diagnosed at 68. Examination reveals a 1.5-cm firm, mobile mass at the 2-o’clock position, 4 cm from the nipple. There is no skin dimpling, nipple discharge, or axillary lymphadenopathy. She is otherwise well and takes only a combined oral contraceptive. She asks whether she can wait for her next routine screening because the mammogram was read as normal. Outside images are available, but no additional views were obtained. The breast center has same-day diagnostic mammography and ultrasound, but MRI slots are booked 3 weeks out.
1. What is the most appropriate next step, and why are repeat screening and immediate MRI not preferred?
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The next step is a diagnostic mammogram of the right breast with spot compression and magnification of the upper outer quadrant, plus targeted ultrasound. A screening mammogram is designed for asymptomatic women and is not adequate to evaluate a palpable mass, especially in heterogeneously dense tissue. Repeating screening would delay diagnosis and may omit needed views. MRI is not first-line for a palpable lump; it is more useful for problem solving after conventional imaging or for high-risk screening. If the diagnostic workup is incomplete, assign BI-RADS 0 and recall; if no abnormality is found, correlate with examination and consider further imaging. She should not wait.
2. Ultrasound shows a 1.2-cm hypoechoic mass with angular margins and posterior acoustic shadowing; no calcifications. What BI-RADS category and tissue sampling method are appropriate?
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The features are suspicious: hypoechoic, angular margins, and posterior shadowing. I would assign BI-RADS 4C, not 5 because classic spiculation or pleomorphic calcifications are absent. Tissue diagnosis should be by image-guided core needle biopsy, preferably 14-gauge ultrasound-guided, with sufficient cores. FNA is less appropriate because it cannot assess architecture or provide a reliable distinction between fibroadenoma and phyllodes tumor. The biopsy result must be concordant with imaging. If the mass is new and palpable, a probably benign label is not appropriate.
3. Core biopsy returns fibroadenoma. Is this concordant? What would you recommend?
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Fibroadenoma would be discordant in a 47-year-old with a new palpable mass and a BI-RADS 4C ultrasound. A benign result does not explain the suspicious morphology. I would review the pathology with a breast pathologist, consider repeat core biopsy or surgical excision, and not simply follow up in 6 months. If excision confirms fibroadenoma, the patient can be reassured, but the discordant imaging finding still requires resolution. This is the key difference between a concordant benign result in a young woman with a classic fibroadenoma and this scenario.