Durable Response to PD1 Inhibitor Pembrolizumab in a Metastatic, Metaplastic Breast Cancer

Elan Gorshein, Kant Matsuda, Gregory Riedlinger, Levi Sokol, Lorna Rodriguez-Rodriguez, Firas Eladoumikdachi, Miral Grandhi, Shridar Ganesan, Deborah L. Toppmeyer, Lindsay Potdevin, Kathleen Toomey, Kim M. Hirshfield, Nancy Chan

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Metaplastic breast cancer (MBC) is a rare and aggressive subtype of breast cancer. Tumor characteristics typically feature estrogen receptor, progesterone receptor, and HER2-negative, triple-negative breast cancer (TNBC), with a poorer prognosis relative to pure invasive ductal or lobular disease. Resistance to chemotherapy often leads to local recurrence and distant metastasis. Genomic profiling has identified multiple molecular abnormalities that may translate to targetable therapies in MBC. These tumors are known to display higher PD-L1 expressivity than other subtypes of breast cancer, and disease control with pembrolizumab and chemotherapy has been documented. We identify a patient with metastatic, metaplastic TNBC, with mesenchymal components and osseous differentiation, who completed 2 years of pembrolizumab treatment and has remained without evidence of disease after 32 months of observation, while maintaining good quality of life. Future efforts should focus on immunotherapy response with respect to the various subtypes of MBC, and treatment should continue to be incorporated in clinical trials to maximize disease response.

Original languageEnglish (US)
Pages (from-to)931-937
Number of pages7
JournalCase Reports in Oncology
Issue number2
StatePublished - Jun 18 2021

All Science Journal Classification (ASJC) codes

  • Oncology


  • Exceptional response
  • Immunotherapy
  • Metaplastic breast cancer
  • Program death ligand-1


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