A 52-year-old woman presents to her primary care physician with a palpable lump in her left breast that she noticed three weeks ago. She denies any breast pain or nipple discharge. She has no family history of breast cancer. Her last mammogram was one year ago and was normal. Vital signs are within normal limits. On physical examination, there is a 3 cm firm, non-tender mass in the upper outer quadrant of the left breast. An ultrasound of the breast reveals a solid mass. A core needle biopsy is performed, and the pathology report confirms the diagnosis.
B) Invasive ductal carcinoma
Invasive ductal carcinoma (IDC) is the most common type of breast cancer, accounting for 70-80% of all breast cancer diagnoses. IDC begins in the milk ducts and then invades the surrounding breast tissue. It can present as a palpable mass and is often detected through imaging studies and confirmed by biopsy.
Answer choice A: Ductal carcinoma in situ (DCIS), is incorrect. DCIS is a non-invasive form of breast cancer that is confined to the ducts and has not invaded surrounding tissue. It is often detected through mammography as microcalcifications.
Answer choice C: Invasive lobular carcinoma, is incorrect. Invasive lobular carcinoma (ILC) is the second most common type of invasive breast cancer but accounts for only about 10-15% of cases. It begins in the lobules and invades surrounding tissue.
Answer choice D: Medullary carcinoma, is incorrect. Medullary carcinoma is a rare subtype of invasive breast cancer that accounts for less than 5% of cases. It has distinct histological features and a better prognosis compared to other types of invasive breast cancer.
Answer choice E: Mucinous carcinoma, is incorrect. Mucinous carcinoma, also known as colloid carcinoma, is a rare subtype of invasive breast cancer that accounts for about 2-3% of cases. It is characterized by the production of mucin.
Key Learning Point
Invasive ductal carcinoma is the most common type of breast cancer, accounting for 70-80% of all breast cancer diagnoses.
