What can the pathologist offer for optimal treatment choice?

Area of Science:

• Oncology
• Pathology
• Translational Medicine

Background:

• Systemic treatment selection for metastatic breast carcinoma is complex.
• Pathologists are crucial for diagnosing metastatic breast carcinoma and evaluating prognostic/predictive biological markers.
• Tumor characteristics can change between primary and metastatic sites, impacting treatment efficacy.

Purpose of the Study:

• To highlight the importance of accurate pathological assessment in guiding systemic therapy for metastatic breast carcinoma.
• To underscore the potential need for re-biopsy of metastatic sites to reassess tumor biological features.
• To emphasize the role of pathologists in ensuring the accuracy and reproducibility of hormone receptor and HER2 assays.

Main Methods:

• Review of current practices in diagnosing and characterizing metastatic breast carcinoma.
• Discussion of the implications of biological changes in tumors during progression.
• Emphasis on the accuracy of diagnostic assays for hormone receptor and HER2 status.

Main Results:

• While most breast carcinomas retain biological features, some metastases exhibit changes necessitating treatment adjustments (endocrine or anti-HER2 therapy).
• Clinical identification of these changing tumors is difficult, making metastasis biopsy valuable for reassessment.
• Factors like intra-tumoural heterogeneity and clonal selection can drive these biological changes.

Conclusions:

• Reassessing biological characteristics of metastatic breast carcinoma via biopsy may be clinically useful.
• Pathologists must strive for maximum accuracy and reproducibility in hormone receptor and HER2 testing to prevent erroneous treatment changes.
• Improving assay procedures is critical to minimize risks associated with false-positive or false-negative results in metastatic breast cancer management.