From the Guidelines
Yes, a ductal carcinoma in situ (DCIS) biopsy can be tested for human epidermal growth factor receptor 2 (HER2). The testing methods used are the same as those for invasive breast cancer, including immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) 1. According to the American Society of Clinical Oncology/College of American Pathologists clinical practice guideline focused update, HER2 testing should be performed using validated IHC assay or in situ hybridization (ISH) 1. The significance of HER2 overexpression in DCIS is still being studied, but it may indicate a more aggressive form of DCIS with higher risk of recurrence or progression to invasive disease. Currently, HER2-targeted therapies like trastuzumab are not standardly recommended for DCIS outside of clinical trials, as the benefit has not been clearly established for this pre-invasive condition 1. Patients should discuss with their oncologist whether HER2 testing of their DCIS specimen would be beneficial for their specific situation and treatment planning. Some key considerations for HER2 testing include:
- The use of consistent and unambiguous standards for reporting HER2 test results 1
- The importance of laboratory accreditation and quality assurance programs for HER2 testing 1
- The need for clinicians to be familiar with the significance of HER2 test results and their implications for patient management 1 It is also worth noting that HER2 testing can be performed on various types of specimens, including surgically excised samples, core biopsies, and cell blocks from fine needle aspiration biopsy (FNAB) 1. However, the specific testing methods and interpretation criteria may vary depending on the type of specimen and the laboratory performing the test. Overall, HER2 testing can be a valuable tool in the management of DCIS, but its use should be carefully considered on a case-by-case basis.
From the Research
DCIS Biopsy and HER2 Testing
- A ductal carcinoma in situ (DCIS) biopsy can be tested for human epidermal growth factor receptor 2 (HER2) 2, 3, 4, 5, 6
- HER2 testing is not currently recommended in DCIS patients according to current practice guidelines, but evidence suggests that HER2-positive DCIS cases may be associated with adverse clinicopathological parameters and increased recurrence rates 2
- Studies have shown that HER2 positivity in DCIS is related to large tumor size, high grade, and ER- and PR negativity 4, 6
Methods for HER2 Testing in DCIS
- Immunohistochemistry (IHC) and chromogenic in situ hybridization (CISH) can be used to detect HER2 gene amplification and protein expression in DCIS specimens 3
- Dual staining technique combining IHC for myoepithelial cells and CISH for HER2 gene can accurately assess HER2 gene status in limited invasive component of DCIS specimens 3
- Silver-enhanced in situ hybridisation (SISH) can also be used for detection of HER2 gene amplification in DCIS specimens 4
Clinical Relevance of HER2 Testing in DCIS
- HER2 positivity in DCIS may be associated with increased risk of ipsilateral recurrence, particularly in situ recurrence 5, 6
- HER2-positive DCIS patients may benefit more from adjuvant radiotherapy, which substantially decreases the local recurrence risk after lumpectomy 5
- HER2 immunohistochemistry on preoperative biopsies may provide useful information to surgeons, favoring wider excisions 5