Evolving paradigms in multifocal breast cancer.

Area of Science:

• Oncology
• Pathology
• Clinical Medicine

Background:

• The 7th edition of the TNM classification defines multifocal breast cancer as multiple, distinct, synchronous ipsilateral lesions.
• Current practice, guided by the College of American Pathologists (CAP), often involves characterizing only the largest lesion.
• This approach simplifies assessment but may not capture the full biological complexity of multifocal disease.

Purpose of the Study:

• To review critical aspects of multifocal breast cancer assessment.
• To highlight the clinical relevance of different intrinsic subtypes within multifocal lesions.
• To discuss the implications of inter-lesion heterogeneity and potential bias in clinical trials.

Main Methods:

• Review of current definitions and clinical practices for multifocal breast cancer.
• Discussion of emerging research on inter-lesion heterogeneity.
• Analysis of the impact of multifocal breast cancer diversity on clinical trial design and interpretation.

Main Results:

• Multifocal breast cancer presents distinct lesions that can harbor different intrinsic subtypes and heterogeneity.
• Current assessment strategies focusing solely on the largest lesion may obscure significant biological differences.
• This simplification risks introducing bias into clinical trials by not accounting for the full spectrum of disease biology.

Conclusions:

• The current approach to multifocal breast cancer assessment, while feasible, may be insufficient given evolving understanding.
• Recognizing inter-lesion heterogeneity and subtype differences is crucial for accurate diagnosis and treatment.
• Future strategies may need to adapt to incorporate the biological diversity of multifocal breast cancers for improved clinical trial validity and patient care.