Uterus, MLH1-deficient endometrioid carcinoma, MLH1 stain [LMP23844]

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Diagnostic Modality: 
Whole Slide Image
Disease Category: 
Genetic Disorders
Diagnosis: 
MLH1-deficient endometrioid carcinoma
Species: 
Human
Organ System: 
Female Genital Tract
Gender: 
Female
Diagnosis Code: 
ICD-10: C54 | ICD-O: 8380/3
Slide Contributor Information
Colgan, T., Nanji, S., Chang, M.

Keywords

mismatch repair, microsatellite instability, Lynch, MLH1, hypermethylation

Clinical History

This section is an MLH1 immunohistochemical stain of an endometrioid carcinoma of the uterus, taken at the time of total abdominal hysterectomy (with bilateral salping-oophorectomy).

Clinical Discussion

Immunohistochemical staining is used to detect abnormalities in mismatch repair, which may reflect microsatellite instability. This pathway is important in Lynch Syndrome: a major cause of hereditary endometrial and colon cancers. In this case, the patient's endometrial carcinoma shows a deficiency in MLH1. This can be caused by either germline mutation of the MLH1 gene (a marker of Lynch Syndrome), or somatic hypermethylation of the gene promoter, leading to loss of expression. Therefore, immunohistochemistry alone cannot confirm Lynch Syndrome in this setting.