Objective:

To report two cases of secretory carcinoma of the breast (SCB), a rare malignancy, and highlight the diagnostic challenges associated with it.

Approach:

• Case Presentations: Two Chinese women with SCB were presented, detailing their tumor characteristics, including size and morphology, immunohistochemistry results, and treatment outcomes.
• Pathological and FISH Methodology: Surgical specimens were processed and analyzed using standardized protocols, including immunohistochemistry and FISH to confirm ETV6-NTRK3 fusion.

Key Findings:

• Both cases exhibited characteristic morphology and a triple-negative immunophenotype.
• ETV6-NTRK3 fusion was confirmed by FISH in both tumors.
• Case 1 had no nodal metastasis, while Case 2 had sentinel lymph node metastasis.

Interpretation:

The findings emphasize the importance of integrating morphology, immunohistochemistry, and molecular confirmation in diagnosing SCB.

Limitations:

• Short-to-intermediate follow-up duration limits conclusions about long-term prognosis.
• Neither patient received TRK inhibitor therapy or had advanced disease.

Conclusion:

The report adds to the understanding of SCB and highlights the need for further research on long-term outcomes and therapeutic options.