To examine and compare human epidermal growth factor receptor 2 (HER2) amplification status in high-grade urothelial carcinoma (HGUCa), using both 2013 and 2018 HER2 reporting guidelines for breast carcinoma from the American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP).
HER2 status by fluorescence in situ hybridization (FISH) assay in 78 cases of HGUCa was compared using 2013 and 2018 HER2 reporting guidelines.
HER2 amplification was observed in 22 (28.2%) of 78 tumors, of which 17 were in group 1, 1 in group 2, and 2 each in groups 3 and 4 (FISH assay, 2018). The remaining 14 HER2-amplified tumors (FISH assay, 2013) became negative, falling into group 2 (FISH assay, 2018) and were either negative or equivocal on immunohistochemistry (IHC, 2018). All FISH-negative tumors (n = 37) using 2013 criteria remained negative (group 5, 2018). FISH-equivocal tumors (2013) were further categorized into HER2 amplified (n = 1) and HER2 negative (n = 4) (2018). Overall, 20 (25.6%) tumors had discordant HER2 FISH results (2018 vs 2013).
Implementing 2018 guidelines, HER2 amplification decreased from 36 to 22 cases. The group with a HER2/CEP17 ratio of 2 or more and average HER2 copy number less than 4 (group 2) were predominantly negative by IHC, suggesting a biologically distinct group of HGUCa that is different from HER2-amplified tumors, which may not respond to HER2-targeted therapy.
American journal of clinical pathology. 2021 Jun 14 [Epub ahead of print]
Sambit K Mohanty, Sourav K Mishra, Ankit Tiwari, Shivani Sharma, Mohit Bhardwaj, Niharika Pattnaik, Sunil Jaiswal, Manas R Baisakh, Subodh Das, Manas R Pradhan, Tapas R Swain, Kaliprasad Satpathy, Sean R Williamson, Anil V Parwani
Department of Pathology and Laboratory Medicine, Advanced Medical Research Institute, Bhubaneswar, India., Department of Medical Oncology, Advanced Medical Research Institute, Bhubaneswar, India., Department of Pathology and Laboratory Medicine, CORE Diagnostics, Gurgaon, India., Department of Surgical Oncology, Advanced Medical Research Institute, Bhubaneswar, India., Department of Pathology and Laboratory Medicine, Prolife Diagnostics, Bhubaneswar, India., Department of Urology, Advanced Medical Research Institute, Bhubaneswar, India., Department of Urology, Kalinga Hospital, Bhubaneswar, India., Department of Pathology, Cleveland Clinic , Cleveland, OH, USA., Department of Pathology, Wexner Medical Center, Ohio State University, Columbus, OH, USA.