Breast Imaging in Focus: Key Pearls from New Guidelines on Proliferative Breast Lesions with Atypia and LCIS

Guidelines for the management of proliferative breast lesions with atypia and lobular carcinoma in situ (LCIS) were recently published in JAMA Surgery and developed collaboratively by the American Society of Breast Surgeons, the Society of Breast Imaging, and the College of American Pathologists.¹

For breast radiologists, there are five key points.

• Rad-path concordance remains central to management.

• Concordant flat epithelial atypia (FEA), atypical lobular hyperplasia (ALH)and classic LCIS generally do not require surgical excision.

• Atypical ductal hyperplasia (ADH) is generally an indication for excision, although carefully selected low-risk cases may be managed with observation.

• Pleomorphic and florid LCIS should be distinguished from classic LCIS because their management is different.

•Breast MRI should not be obtained automatically simply because one of these lesions is diagnosed.

How to Address Flat Epithelial Atypia (FEA)

If FEA is the highest order finding on core biopsy and concordant with the imaging findings, diagnostic excision is generally not indicated. No additional diagnostic imaging is required, and patients may return to age-appropriate screening.

Flat epithelial atypia alone also does not warrant supplemental MRI.

A second pathology review should be considered for FEA, particularly in non-specialized pathology practices, because FEA may be reclassified as a higher-order lesion such as ADH.

What Do the Guidelines Recommend for Atypical Ductal Hyperplasia (ADH)?

The guideline cites a pooled upgrade rate of approximately 29 percent to DCIS or invasive carcinoma. Therefore, diagnostic excision should generally be considered. However, carefully selected patients may be considered for observation.

The criteria for considering observation include:

• No palpable mass.

• Mammographic calcifications only, without an associated mass, asymmetry, or architectural distortion.

• Focal ADH involving no more than two terminal ductal lobular units.

• Greater than 50 percent sampling of the target calcifications.

• Rad-path concordance.

Multidisciplinary input from radiology, pathology, and surgery is recommended when considering observation.

A second pathology review is also recommended to confirm ADH because of diagnostic variability between ADH and low-grade DCIS.

For patients managed with observation, a six-month follow-up mammogram may be considered before returning to age-appropriate screening.

Importantly, most evidence supporting observation comes from mammographically-detected ADH. Data for MRI-detected ADH are limited, and excision may still be considered in this setting.

How Should Physicians Approach Lobular Neoplasia?

For lobular neoplasia, the key distinction is between ALH and classic LCIS versus pleomorphic and florid LCIS.

Concordant ALH and classic LCIS generally do not require diagnostic excision. As with ADH, however, most evidence supporting observation comes from mammographically detected lesions, and data for MRI-detected lobular neoplasia remain limited.

Pleomorphic and florid LCIS should be managed differently. These lesions should undergo diagnostic excision, and negative margins should be achieved.

Keys to Assessing Future Breast Cancer Risk

Atypical ductal hyperplasia, ALH, and classic LCIS are associated with increased future breast cancer risk. Patients with these diagnoses should undergo comprehensive risk assessment and counseling regarding risk-reducing strategies.

Flat epithelial atypia is different. FEA alone does not appear to increase future breast cancer risk and is not by itself an indication for supplemental MRI surveillance.

What Do the Guidelines Recommend on the Role of Breast MRI?

More broadly, these guidelines emphasize that MRI should not be performed simply because a high-risk lesion has been diagnosed. For example, MRI is not recommended after a diagnosis of ADH solely to evaluate for occult malignancy or determine whether excision is necessary.

Instead, surveillance MRI should be considered based on the patient's overall breast cancer risk rather than the biopsy diagnosis alone.

In Conclusion

• Concordant FEA, ALH, and classic LCIS generally do not require surgical excision.

• ADH generally does require excision, although carefully selected low-risk cases may be observed.

• Pleomorphic and florid LCIS require surgical excision with negative margins.

• Across all of these diagnoses, rad-path concordance and sampling adequacy are critical. If pathology is discordant with imaging findings, additional sampling is recommended.

These recommendations are evidence-informed and consensus-based, and multidisciplinary clinical judgment remains important.

Dr. Bahl is an associate professor at Harvard Medical School and a breast radiologist affiliated with Massachusetts General Hospital.

Reference

1. Nakhlis F, Bedrosian I, King TA, et al. American Society of Breast Surgeons, Society of Breast Imaging, and College of American Pathology 2026 guidelines for the management of proliferative lesions with atypia and lobular carcinoma in situ. JAMA Surg. 2026 Aug 19. doi: 10.1001/jamsurg.2026.3552. Online ahead of print.