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Updated: Jun 6, 2025
A Robust Discovery Platform for the Identification of Novel Mediators of Melanoma Metastasis
Published on: March 8, 2022
Study of Microsatellite Instability by Immunohistochemistry in a Cohort of Patients With Melanoma
Rodolfo David Palacios Diaz1, Blanca de Unamuno Bustos1,2, Mónica Pozuelo Ruiz1
1Dermatology Department, Hospital Universitari i Politècnic La Fe, Valencia, Spain.
Background:
Microsatellite instability (MSI) has prognostic value and impacts therapy strategies in several malignancies. Data regarding MSI in melanoma are scarce. The aim of this study was to assess MSI through the analysis of MMR protein expression in patients with melanoma.
Methods:
An observational retrospective single-center study was designed based on patients with primary melanoma. We assessed MSI through immunohistochemical staining with anti-MLH1, anti-MSH2, anti-MSH6, and anti-PMS2 on full-thickness excision tissue.
Results:
Ninety-three patients were included in this study. The complete absence of nuclear staining in tumoral cells was extremely rare, with only one melanoma not expressing MSH6. Most melanomas showed an expression index for MLH1 (77.7%), MSH2 (87.2%), and PMS2 (78.6%) ≥ 75%. Most melanomas (57.8%) exhibited an MSH6 expression index in the range of 1%-74%. A low MSH6 expression index and a reduced combined MMR protein expression index (MMR-e) were significantly associated with higher melanoma-specific survival. A mild PMS2 staining intensity was significantly associated with a higher melanoma-specific survival. The patients with high MMR-e who received immunotherapy progressed and died more frequently than those with reduced MMR-e (75% vs. 33.3%).
Conclusion:
More studies are needed to further define the role of MSI in melanoma prognosis and response to immunotherapy.
