A 52-year-old woman presents for her routine annual mammogram. She has no symptoms such as breast pain, lumps, or nipple discharge and no significant family history of breast or ovarian cancer. Her mammogram reveals suspicious lesions in the upper outer quadrant of the left breast. A stereotactic core needle biopsy confirms high-grade ductal carcinoma in situ (DCIS) with comedo necrosis, and the tumor is estrogen receptor-positive (ER+). She undergoes a lumpectomy. What is the hallmark mammographic finding in ductal carcinoma in situ (DCIS)?
