Department of Internal Medicine, The Ohio State University Wexner Medical Center, The Ohio State University Comprehensive Cancer Center, Columbus, OH, USA.
Department of Pathology, The Ohio State University Wexner Medical Center, Columbus, OH, USA.
Mod Pathol. 2018 Dec;31(12):1891-1900. doi: 10.1038/s41379-018-0058-y. Epub 2018 Jul 2.
Universal screening for Lynch syndrome in colorectal cancer is recommended, and immunohistochemistry for the mismatch repair proteins is commonly used. To reduce cost, some screen using only MSH6 and PMS2, with reflex to the partner stain if either are absent (two-stain method). An expression pattern revealing absent MSH2 and intact MSH6 is not expected, but could result in failed Lynch syndrome detection. We analyzed tumors with absent MSH2 but any degree of MSH6 expression to determine if the two-stain method could miss MSH2 mutations. One-thousand seven-hundred thirty colorectal cancer patients from the Ohio Colorectal Cancer Prevention Initiative underwent tumor screening using microsatellite instability and immunohistochemistry. The two-stain method was used for 1235 cases; staining for all four proteins was completed for 495 cases. The proportion of positive cells and staining intensity were reviewed for MSH6, as well as MSH2 when available. Patients with mismatch repair deficiency underwent next-generation sequencing of germline DNA for mismatch repair genes. If negative, tumor next-generation sequencing was performed to assess for somatic mutations. Overall, thirty-three (1.9%, 33/1730) MSH2-absent cases were identified. Of those, fourteen had no MSH6 expression but eight (0.5%, 8/1730) had ambiguous and eleven (0.6%, 11/1730) had convincing MSH6 expression that could have been interpreted as intact. Germline next-generation sequencing identified MSH2 mutations in 11/14 cases with absence of both stains, 7/8 cases with ambiguous MSH6 expression, and 9/11 cases with convincing MSH6 expression. All remaining cases, except one, had double somatic mutations. The two-stain method fails to detect some patients with Lynch syndrome: (1) significant staining weaker than the control may be incorrectly interpreted as intact MSH6, or (2) Weak or focal/patchy MSH6 can be retained with the absence of MSH2. Accordingly, we recommend the four-stain method be used for optimal Lynch syndrome screening detection.
建议对结直肠癌进行林奇综合征的普遍筛查，常用免疫组化检测错配修复蛋白。为了降低成本，一些筛查仅使用 MSH6 和 PMS2，如果任一缺失则进行互补染色（两染法）。不期望出现 MSH2 缺失而 MSH6 完整的表达模式，但可能导致林奇综合征漏检。我们分析了 MSH2 缺失但 MSH6 有不同程度表达的肿瘤，以确定两染法是否会漏检 MSH2 突变。俄亥俄州结直肠癌预防计划的 1730 例结直肠癌患者接受了微卫星不稳定性和免疫组化肿瘤筛查。1235 例采用两染法，495 例完成了所有四种蛋白的染色。评估了 MSH6 的阳性细胞比例和染色强度，并在有 MSH2 时也评估了 MSH2。错配修复缺陷的患者接受了错配修复基因的种系 DNA 下一代测序。如果阴性，进行肿瘤下一代测序以评估体细胞突变。总体而言，鉴定出 33 例（1.9%，33/1730）MSH2 缺失病例。其中，14 例无 MSH6 表达，但 8 例（0.5%，8/1730）表达不明确，11 例（0.6%，11/1730）表达有说服力，可能被解释为完整。种系下一代测序在 14 例两染均缺失的病例中鉴定出 MSH2 突变，在 7 例 MSH6 表达不明确的病例中和在 9 例 MSH6 表达有说服力的病例中鉴定出 MSH2 突变。除 1 例外，所有其余病例均有双体细胞突变。两染法未能检测到一些林奇综合征患者：（1）明显弱于对照的染色可能被错误地解释为 MSH6 完整，或（2）MSH2 缺失时可保留弱或局灶/斑驳的 MSH6。因此，我们建议使用四染法进行最佳的林奇综合征筛查检测。
