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Diamond: immunohistochemistry versus sequencing in EGFR analysis of lung adenocarcinomas
  1. Moira Ragazzi1,
  2. Ione Tamagnini1,
  3. Alessandra Bisagni1,
  4. Alberto Cavazza1,
  5. Maria Pagano2,
  6. Licia Baldi2,
  7. Corrado Boni2,
  8. Flavia Cantile3,
  9. Fausto Barbieri3,
  10. Davide Nicoli4,
  11. Giuliana Sartori5,
  12. Dario de Biase6,
  13. Giorgio Gardini1,
  14. Giulio Rossi7
  1. 1Department of Oncology and Advanced Technologies, Operative Unit of Pathology, Azienda S Maria Nuova – IRCCS, Reggio Emilia, Italy
  2. 2Department of Oncology and Advanced Technologies, Operative Unit of Oncology, Azienda S. Maria Nuova – IRCCS, Reggio Emilia, Italy
  3. 3Department of Oncology and Hematology, Division of Oncology, Azienda Ospedaliero-Universitaria Policlinico, Modena, Italy
  4. 4Department of Oncology and Advanced Technologies, Operative Unit of Molecular Biology, Azienda S. Maria Nuova – IRCCS, Reggio Emilia, Italy
  5. 5Department of Oncology and Advanced Technologies, Cervical Screening Unit, Azienda S. Maria Nuova – IRCCS, Reggio Emilia, Italy
  6. 6Department of Medicine (DIMES), Anatomic Pathology Unit, Bellaria Hospital, University of Bologna, Bologna, Italy
  7. 7Integrated Department of Diagnostic Laboratories, Section of Pathologic Anatomy, Azienda Ospedaliero-Universitaria Policlinico, Modena, Italy
  1. Correspondence to Dr Moira Ragazzi, Department of Oncology and Advanced Technologies; Operative Unit of Pathology, Azienda S. Maria Nuova/IRCCS; Viale Risorgimento 80, Reggio Emilia 42123, Italy; moira.ragazzi{at}asmn.re.it

Abstract

Aims Identification of epidermal growth factor receptor (EGFR) mutations in lung adenocarcinomas is the single most important predictor of clinical response and outcome using EGFR tyrosine kinase inhibitors (TKIs). EGFR E746-A750del and L858R mutations are the most common gene alterations, also predicting the best clinical response to TKIs. We evaluated the accuracy of EGFR mutation-specific antibodies in a large cohort of lung adenocarcinomas, with different molecular settings and types of tissue samples.

Methods 300 lung adenocarcinomas diagnosed on cytology (48 cell blocks), biopsy (157 cases) and surgical resections (95 cases) were selected. All cases were investigated for EGFR by sequencing and two mutation-specific antibodies (clone 6B6 for E746-A750del; clone 43B2 for L858R) were tested using an automated immunostainer. Discordant results were investigated by next-generation sequencing (NGS).

Results Overall sensitivity and specificity of mutant-specific antibodies were 58.6% and 98.0%, respectively, and they increased up to 84% and 100% if only tumours harbouring E746-A750del were considered. In 13 discordant cases, NGS confirmed immunohistochemistry results in eight samples.

Conclusions The EGFR mutation-specific antibodies have a fair/good sensitivity and good/high specificity in identifying classic mutations, but they cannot replace molecular tests. The antibodies work equally well on biopsies and cell blocks, possibly permitting a rapid screening in cases with poor material.

  • EGFR
  • IMMUNOHISTOCHEMISTRY
  • LUNG
  • LUNG CANCER

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