A Case of HER2-positive Metaplastic Breast Cancer whose Subtype Changed to Triple-negative after Anti-HER2 Therapy

Key Points

• To report on a rare case of HER2-positive metaplastic breast cancer that transformed to triple-negative after treatment.
• Case report of an 80-year-old female with a HER2-positive metaplastic breast cancer
• Initial diagnosis included imaging and biopsy confirming the type
• Treatment involved surgery followed by anti-HER2 therapy
• Monitoring of tumor subtype changes over the treatment period
• Initial identification as HER2-positive metaplastic breast cancer
• After anti-HER2 therapy, skin recurrence showed transformation to triple-negative subtype
• Late-stage intervention was challenged by tumor heterogeneity