Abstract
BackgroundHER2 assessment in biopsy specimens of gastric cancer (GC) is challenging because of the intratumoral heterogeneity. False negative results may be get because of limited biopsy material. The aim of this study is to explore how tumor-containing fragment number and biopsy specimen number affect HER2 immunohistochemistry (IHC) positive rate.MethodsEight hundred and ninety biopsy specimens and 459 paired resected specimens were collected. IHC staining of HER2 was performed. HER2 IHC positive (scored 3+) rate was compared based on tumor-containing fragment number, biopsy specimen number, average size and tumor tissue proportion of tumor-containing fragments. The positive predictability of biopsy specimens to resected specimens was analyzed based on tumor fragment number.ResultsHER2 IHC positive rates were 2.0, 3.5, 7.0, 13.2, 17.1, and 15.9% when tumor fragment numbers were 1, 2, 3, 4, 5 and 6 respectively. The rate rose with the increase of tumor fragment number (P = 0.004). ROC curve analysis showed that biopsy specimens exhibited positive predictability when tumor fragment number reached 3, but showed better performance when the number was ≥4 (P < 0.05). After fragment number reached 4, no statistic differences were reached in either HER2 IHC positive rate or positive predictability with further increase of the number (P > 0.05). HER2 IHC positive rate was not associated with biopsy number (P = 0.127), average size of tumor fragments (P = 0.397), and tumor tissue proportion of tumor fragments (P = 0.825) directly.ConclusionsThe number of tumor-containing fragments influences HER2 IHC positive (scored 3+) rate. Greater than or equal to 4 (≥4) tumor fragments give better results in the positive rate as well as positive predictability. We recommend the number of tumor containing fragments be described in the HER2 IHC pathology reports for clinical reference in endoscopic biopsy specimens of GC.
Highlights
human epidermal growth factor receptor 2 (HER2) assessment in biopsy specimens of gastric cancer (GC) is challenging because of the intratumoral heterogeneity
Accurate assessment of human epidermal growth factor receptor 2 (HER2) is a pivotal issue in gastric cancer (GC) since the Trastuzumab for Gastric Cancer (ToGA) trial proved the value of the targeted therapy in HER2 positive GC patients [1]
Many GC patients are with inoperable lesions and endoscopic biopsy becomes the only available approach to obtain tumor tissues for HER2 assessment
Summary
HER2 assessment in biopsy specimens of gastric cancer (GC) is challenging because of the intratumoral heterogeneity. The aim of this study is to explore how tumor-containing fragment number and biopsy specimen number affect HER2 immunohistochemistry (IHC) positive rate. Accurate assessment of human epidermal growth factor receptor 2 (HER2) is a pivotal issue in gastric cancer (GC) since the Trastuzumab for Gastric Cancer (ToGA) trial proved the value of the targeted therapy in HER2 positive GC patients [1]. Many GC patients are with inoperable lesions and endoscopic biopsy becomes the only available approach to obtain tumor tissues for HER2 assessment. Biopsy specimens are with more influence factors and in turn more difficult to manipulate [2]. It is of clinical importance to explore influential factors and optimize HER2 detection in biopsy specimens. Several approaches are available for HER2 status assessment, including immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and silver in situ hybridization (SISH). IHC represents an effective and robust test that can be used for most specimens [3], and has been proved to be a valuable approach in reflecting HER2 status in GC [1, 4]
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