Robertson Scott A, Cimino-Mathews Ashley, Cornish Toby C
Departments of Pathology.
Oncology, Johns Hopkins School of Medicine, Baltimore, MD.
Appl Immunohistochem Mol Morphol. 2018 Jan;26(1):35-39. doi: 10.1097/PAI.0000000000000382.
Semiquantitative immunohistochemistry (IHC) is commonly used in combination with fluorescence in situ hybridization (FISH) to detect HER2 amplification in gastroesophageal adenocarcinomas. Most laboratories apply these tests in a sequential algorithm, using IHC as a frontline test and reserving FISH for IHC-equivocal cases. To gain a better understanding of the concordance of IHC and FISH results at our institution, we identified all gastroesophageal adenocarcinomas at our institution tested for HER2 (n=125). Matched IHC and FISH were available for 116 cases (94%). Cases consisted of adenocarcinoma of the distal esophagus (22%), gastroesophageal junction (24%), stomach (43%), and metastatic sites (12%). A total of 88 cases (70%) were biopsies, whereas 37 cases (30%) were resections. Overall, 15 cases (13%) were HER2 positive (IHC 3+ and/or FISH amplified). A total of 60 cases (52%) were IHC score 0; none of these were HER2 amplified by FISH. A total of 30 cases (26%) were IHC 1+; 5 (17%) of these cases were HER2 amplified by FISH. A total of 20 cases (17%) were IHC 2+; 4 (20%) of these cases were HER2 amplified by FISH. A total of 6 cases were IHC score 3+; all of these were HER2 amplified by FISH. Although there was a high overall concordance between IHC and FISH results (96%), a subset (17%) of IHC-negative cases (score 1+) were HER2 amplified as evaluated by FISH, representing 33% of all HER2 amplified cases. This suggests that the common practice of limited FISH testing to IHC 2+ cases will miss a significant number of HER2 amplified cases.
半定量免疫组织化学（IHC）通常与荧光原位杂交（FISH）联合使用，以检测胃食管腺癌中的HER2扩增。大多数实验室采用序贯算法进行这些检测，将IHC作为一线检测方法，仅对IHC结果不明确的病例进行FISH检测。为了更好地了解我们机构中IHC和FISH结果的一致性，我们确定了本机构所有检测过HER2的胃食管腺癌病例（n = 125）。116例（94%）病例有匹配的IHC和FISH结果。病例包括远端食管癌（22%）、胃食管交界癌（24%）、胃癌（43%）和转移部位癌（12%）。共有88例（70%）为活检病例，37例（30%）为切除病例。总体而言，15例（13%）为HER2阳性（IHC 3+和/或FISH扩增）。共有60例（52%）IHC评分为0；这些病例中无一例FISH检测显示HER2扩增。共有30例（26%）为IHC 1+；其中5例（17%）FISH检测显示HER2扩增。共有20例（17%）为IHC 2+；其中4例（20%）FISH检测显示HER2扩增。共有6例IHC评分为3+；所有这些病例FISH检测均显示HER2扩增。尽管IHC和FISH结果总体一致性较高（96%），但FISH检测显示，IHC阴性病例（评分为1+）中有一部分（17%）存在HER2扩增，占所有HER2扩增病例的33%。这表明，仅对IHC 2+病例进行有限的FISH检测这一常见做法会遗漏大量HER2扩增病例。
