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USMLE® Step 2 Question of the Day: Pleomorphic microcalcifications

Osmosis Team
Feb 7, 2024

We're back with a USMLE® Step 2 CK Question of the Day! Today's case involves a 48-year-old woman with no breast symptoms, a history of PCOS, and family history of ovarian cancer presents with mammographic microcalcifications. What's the best next step in her management? Can you figure it out?

A 48-year-old woman presents to the primary care clinic for a routine mammogram. The patient has not had breast pain, nipple discharge, skin changes, or breast masses on self-examination. Past medical history is significant for polycystic ovarian syndrome (PCOS) for which she has been taking oral contraceptive pills for 20 years. She has never been pregnant. Family history is significant for ovarian cancer in her maternal aunt at the age of 51. BMI is 24 kg/m2. Vital signs are within normal limits. Physical examination is unremarkable. Mammography reveals several clusters of fine, pleomorphic microcalcifications in the upper outer quadrant of the right breast. Diagnostic bilateral mammography confirms these findings. Which of the following is the best next step in management?

A. Core needle biopsy

B.  Close follow-up with repeat mammography in 6 months

C. MRI of the right breast

D. Surgical excisional biopsy

E. PET CT scan

Scroll down for the correct answer!

The correct answer to today's USMLE® Step 2 CK Question is...

A. Core needle biopsy

Before we get to the Main Explanation, let's see why the answer wasn't B, C, D, or E. Skip to the bottom if you want to see the correct answer right away!

Incorrect answer explanations

Today's incorrect answers are...

B. Close follow-up with repeat mammography in 6 months

Incorrect: Close follow-up with repeat mammography in 6 months is not appropriate in this case due to the presence of findings specific for DCIS (pleomorphic microcalcifications) on the initial mammogram. These findings warrant further evaluation with a core needle biopsy.

C. MRI of the right breast

Incorrect: Breast MRI can be used in addition to mammography for screening in certain high-risk patients or it can be ordered to better assess known malignancies. However, it does not replace biopsy for confirming the diagnosis of DCIS. Definitive diagnosis of DCIS requires a histologic sample obtained most often with a core needle biopsy.

D. Surgical excisional biopsy

Incorrect: Core needle biopsy is the preferred initial biopsy approach as it is less invasive than surgical excisional biopsy. Surgical excisional biopsy might be considered if the core needle biopsy does not provide a clear diagnosis, or if the lesion is inaccessible.

E. PET CT scan

Incorrect: A PET CT scan is not part of the initial assessment for a suspicious finding on a mammogram. PET scans are used to determine the extent of established malignancies and to detect metastasis.

Main Explanation

This patient presents with mammographic findings of clusters of fine pleomorphic microcalcifications, which are highly suggestive of ductal carcinoma in situ. The best next step in the evaluation is to obtain tissue diagnosis and assess the degree of tissue invasion with a core needle biopsy. If neoplastic epithelial cells arise from ductal tissue without invasion of the basement membrane, ductal carcinoma in situ can be diagnosed.

Mammography is a crucial tool in the early detection of breast cancer. If findings suspicious of malignancy are found on screening mammography, then bilateral diagnostic mammography should be performed next. The presence of microcalcifications on a mammogram, particularly those with a fine pleomorphic, fine linear, or branching pattern, most often indicates DCIS. Additional indications of malignancy include architectural distortion or soft tissue masses. 

By definition, DCIS (ductal carcinoma in situ) is composed of neoplastic epithelial cells confined within the breast ductal system. Core needle biopsy is indicated to confirm the presence of neoplastic epithelial cells arising from ductal tissue without invasion through the basement membrane. Once confirmed with tissue biopsy, staging is done and hormone receptor status should be determined. Consultation with a geneticist may be necessary as well. Knowing the hormone receptor status helps to guide future therapies, while genetic counseling is important for patients who may have inherited genetic mutations.

core needle biopsy illustration

Major takeaway

Patients with screening mammographic findings of microcalcifications should have a diagnostic bilateral mammogram and core needle biopsy. Distinguishing between DCIS and invasive carcinoma involves histological analysis to determine whether neoplastic epithelial cells have invaded through the basement membrane of the ductal system.


Gradishar WJ, Moran MS, Abraham J, et al. Breast Cancer, Version 3.2022, NCCN Clinical Practice Guidelines in Oncology. J Natl Compr Canc Netw. 2022;20(6):691-722. doi:10.6004/jnccn.2022.0030


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