Novel uses of immunohistochemistry in breast pathology: interpretation and pitfalls

Mod Pathol. 2021 Jan;34(Suppl 1):62-77. doi: 10.1038/s41379-020-00697-3. Epub 2020 Oct 27.

Abstract

Immunohistochemistry is an essential component of diagnostic breast pathology. The emergence of novel assays and applications is accompanied by new interpretation criteria and potential pitfalls. Immunohistochemistry assists in supporting breast origin for primary or metastatic carcinomas and identifying non-mammary metastases to the breast; however, no single immunostain is perfectly sensitive nor specific. GATA3 and Sox10 are particularly useful immunostains to identify triple negative breast carcinoma, which are often negative for other markers of mammary differentiation. Sox10 labeling is a major potential diagnostic pitfall, as Sox10 and S-100 label both triple negative breast carcinoma and metastatic melanoma; a pan-cytokeratin immunostain should always be included for this differential diagnosis. Novel immunohistochemistry serves as surrogates for the molecular alterations unique to several of special-type breast carcinomas, including the use of MYB in adenoid cystic carcinoma, pan-TRK in secretory carcinoma, and mutant IDH2 in tall cell carcinoma with reversed polarity (TCCRP). In addition, PD-L1 immunohistochemistry is an emerging, albeit imperfect, biomarker for breast cancer immunotherapy, with different assay parameters and scoring criteria in breast carcinoma compared to other tumor types. The expanding repertoire of novel immunohistochemistry provides additional diagnostic tools and biomarkers that improve diagnostic breast pathology and patient care.

Publication types

  • Review

MeSH terms

  • B7-H1 Antigen
  • Biomarkers, Tumor / analysis
  • Breast / pathology
  • Breast Neoplasms* / diagnosis
  • Breast Neoplasms* / pathology
  • Carcinoma / diagnosis
  • Carcinoma / pathology
  • Carcinoma, Adenoid Cystic / diagnosis
  • Carcinoma, Adenoid Cystic / pathology
  • Carcinoma, Ductal, Breast / diagnosis
  • Carcinoma, Ductal, Breast / pathology
  • Diagnosis, Differential
  • Female
  • GATA3 Transcription Factor / analysis
  • Humans
  • Immunohistochemistry / methods*
  • SOXE Transcription Factors / analysis
  • Triple Negative Breast Neoplasms / diagnosis
  • Triple Negative Breast Neoplasms / pathology

Substances

  • B7-H1 Antigen
  • Biomarkers, Tumor
  • GATA3 Transcription Factor
  • SOXE Transcription Factors

Supplementary concepts

  • Secretory breast carcinoma