The Conjoint Gastroenterology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia.
Faculty of Medicine, University of Queensland, Brisbane, QLD, Australia.
Mod Pathol. 2017 Dec;30(12):1728-1738. doi: 10.1038/modpathol.2017.92. Epub 2017 Jul 28.
Sessile serrated adenomas are the precursor polyp of approximately 20% of colorectal carcinomas. Sessile serrated adenomas with dysplasia are rarely encountered and represent an intermediate step to malignant progression, frequently associated with loss of MLH1 expression. Accurate diagnosis of these lesions is important to facilitate appropriate surveillance, particularly because progression from dysplasia to carcinoma can be rapid. The current World Health Organization classification describes two main patterns of dysplasia occurring in sessile serrated adenomas, namely, serrated and conventional. However, this may not adequately reflect the spectrum of changes seen by pathologists in routine practice. Furthermore, subtle patterns of dysplasia that are nevertheless associated with loss of MLH1 expression are not encompassed in this classification. We performed a morphological analysis of 266 sessile serrated adenomas with dysplasia with concurrent MLH1 immunohistochemistry with the aims of better defining the spectrum of dysplasia occurring in these lesions and correlating dysplasia patterns with MLH1 expression. We found that dysplasia can be divided morphologically into four major patterns, comprising minimal deviation (19%), serrated (12%), adenomatous (8%) and not otherwise specified (79%) groups. Minimal deviation dysplasia is defined by minor architectural and cytological changes that typically requires loss of MLH1 immunohistochemical expression to support the diagnosis. Serrated dysplasia and adenomatous dysplasia have distinctive histological features and are less frequently associated with loss of MLH1 expression (13 and 5%, respectively). Finally, dysplasia not otherwise specified encompasses most cases and shows a diverse range of morphological changes that do not fall into the other subgroups and are frequently associated with loss of MLH1 expression (83%). This morphological classification of sessile serrated adenomas with dysplasia may represent an improvement on the current description as it correlates with the underlying mismatch repair protein status of the polyps and better highlights the range of morphologies seen by pathologists.
无蒂锯齿状腺瘤是大约 20%结直肠癌的前体息肉。有异型增生的无蒂锯齿状腺瘤很少见，代表恶性进展的中间步骤，常伴有 MLH1 表达缺失。准确诊断这些病变对于促进适当的监测很重要，特别是因为异型增生向癌的进展可能很快。目前的世界卫生组织分类描述了无蒂锯齿状腺瘤中两种主要的异型增生模式，即锯齿状和传统型。然而，这可能不能充分反映病理学家在常规实践中看到的变化谱。此外，与 MLH1 表达缺失相关的微妙异型增生模式也不包括在该分类中。我们对 266 例伴有 MLH1 免疫组化的有异型增生的无蒂锯齿状腺瘤进行了形态学分析，目的是更好地定义这些病变中发生的异型增生谱，并将异型增生模式与 MLH1 表达相关联。我们发现，异型增生在形态上可分为四个主要类型，包括最小偏差（19%）、锯齿状（12%）、腺瘤性（8%）和非特指（79%）组。最小偏差异型增生的定义是轻微的结构和细胞学改变，通常需要 MLH1 免疫组化表达缺失来支持诊断。锯齿状异型增生和腺瘤性异型增生具有独特的组织学特征，较少与 MLH1 表达缺失相关（分别为 13%和 5%）。最后，非特指异型增生包含了大多数病例，显示出广泛的形态变化，不属于其他亚组，并且常与 MLH1 表达缺失相关（83%）。这种有异型增生的无蒂锯齿状腺瘤的形态学分类可能优于目前的描述，因为它与息肉的错配修复蛋白状态相关，并且更好地突出了病理学家看到的形态变化范围。
