4.

两种方法检测结果错误诊断的原因分析

Analysis of causes of misdiagnosis by the two methods

Cause	Misdiagnosis	n
Immunohistochemical weak staining led to dMMR misdiagnosis; High background staining of IHC led to pMMR misdiagnosis; Specimen contamination led to MSI-H false positives; The lack of tumor cells led to MSS false negatives.
Immunohistochemical weak staining	dMMR misdiagnosis	2
IHC high background staining	pMMR misdiagnosis	1
Specimen contamination	MSI-H false positives	5
Tumor cells lack	MSS false negatives	2