HISTOLOGICAL CHARACTERISTICS AND ASSESSMENT OF MLH1 EXPRESSIONS ON SERRATED LESION/POLYP BY WHO 2019

Hữu Thái Trần1,, Phúc Thịnh Ngô2, Thanh Phượng Huỳnh3, Thị Ngọc Diễm Võ 3
1 Da Nang hospital
2 City University of Medicine and Pharmacy Hospital. Ho Chi Minh
3 University of Medicine and Pharmacy at Ho Chi Minh City

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Abstract

Background: 2019 WHO classification, there have been important changes in histopathology diagnostic criteria for serrated lesions/polyps of colorectal and the role of MLH1 in the diagnosis of sessile serrated lesions with dysplasia (SSLD). Objectives: (1) Describe the characteristics of histopathology according to WHO 2019 updates of serrated lesions/polyps (2) Evaluate the expression of MLH1 on serrated lesions (SSL) and SSLD. Methods: 136 cases/130 patients are screened by diagnostic, keywords, and images from 1915 cases that have been first diagnosed as serrated lesions/polyps at the Department of Embryology, Histology, and Pathology, Ho Chi Minh City University of Medicine and Pharmacy from 01/2019 to 05/2021. Evaluate the manifestation of MLH1 on 29 cases of SSL and SSLD. Results: In the SSL diagnostic criteria, the most asymmetrical proliferation (86.2%), the least common horizontal growth along muscularis mucosa (27.6%), serration extending into the crypt base, and dilation of the crypt base is about half of the case (48.3% - 65.5%). In SSLD the most common dysplasia is not otherwise specified morphology (66.7%), 25% minimal deviation dysplasia, and the least common serrated dysplasia (8.3%). 100% of TSA cases present two characteristics: slit-like serrations and unique cytological features, 38.7% have no characteristics of ectopic crypt formation, and 25.8% TSA arising from a precursor lesion. MLH1 loss is not recorded in 29 cases of SSL and SSLD. Conclusions: The study showed the histopathological characteristics of serrated lesions/polyps in the colorectum as updated by WHO 2019. However, poor tissue sample orientation may affect the frequency of important diagnostic features, This shows the important role of sample orientation. Slit-like serration and typical cytology are two specific features in the diagnosis of TSA. No loss of MLH1 expression was recorded in SSL and SSLD, possibly due to the small sample size and poor sample quality affecting the staining results.

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References

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