Characterization of Paired Box 8 (PAX8)-expressing Metastatic Breast Carcinoma

Area of Science:

• Oncology
• Pathology
• Cancer Biomarkers

Background:

• Paired box 8 (PAX8) is an organ-specific marker used to differentiate Müllerian and breast carcinomas.
• PAX8 expression in a subset of breast carcinomas can lead to diagnostic challenges in determining cancer origin.
• Understanding PAX8 expression in metastatic breast carcinomas (MBCs) is crucial for accurate diagnosis.

Purpose of the Study:

• To investigate the characteristics of PAX8-expressing MBCs.
• To assess the diagnostic implications of PAX8 expression in distinguishing primary versus metastatic breast cancer.
• To elucidate the primary site of occurrence in cases of PAX8-positive metastatic breast carcinoma.

Main Methods:

• Immunohistochemistry was employed to evaluate PAX8 status.
• PAX8 expression was examined in 80 MBCs and 52 matched primary breast carcinomas (PBCs).

Main Results:

• 20% of MBCs exhibited PAX8 expression.
• A high concordance rate (92.3%) of PAX8 expression was observed between MBCs and PBCs.
• PAX8 expression in MBCs was significantly associated with high-grade features and negative estrogen/progesterone receptor status.

Conclusions:

• PAX8 can be detected in MBCs, particularly those with high-grade and non-luminal molecular subtypes.
• Reliance solely on PAX8 positivity for determining the primary tumor site requires careful evaluation.
• Further research is needed to refine diagnostic criteria for PAX8-expressing breast cancers.