Which marker pattern is most consistent with breast origin when GATA3 is positive and ER/PR/HER2 status may vary?

• A. GATA 3+, ER/PR/HER2(-/+)
• B. Napsin A +, TTF-1 +
• C. Napsin A +, GATA3 -
• D. GATA3 +, Napsin A-

Answer: (A)

GATA3 positivity is a strong indicator of breast origin in metastatic tumors, because GATA3 is a sensitive marker for breast (and urothelial) carcinomas. The ER, PR, and HER2 status, however, can vary widely among breast cancers—they may be positive in some tumors and negative in others, or show mixed results across receptors. So a pattern where GATA3 is positive and the receptor status is variable fits the typical breast profile: the tumor shows a breast-associated marker, while receptor expression isn’t uniform.

In contrast, markers like Napsin A and TTF-1 point toward lung origin when they are positive, so those patterns would be less consistent with breast origin. If Napsin A is positive (especially with GATA3 negative or ambiguous results), that would more likely reflect a lung primary. Therefore the combination of GATA3 positivity with variable ER/PR/HER2 status best supports breast origin.