MTAP Staining Confirms Gene Deletion in Mesothelioma, but Normal Expression Does Not Rule It Out
Researchers at Brigham and Women's Hospital examined 40 malignant pleural mesothelioma tumors using targeted next-generation sequencing and single-nucleotide polymorphism microarray. Loss of MTAP protein expression was 100% specific for CDKN2A deletion but only 59% sensitive. The reason: many tumors carried heterozygous deletions that left partial protein expression intact. Among the 40 tumors, 27 showed CDKN2A deletion and 20 of those also had MTAP codeletion. No tumor showed MTAP deletion without CDKN2A codeletion. Homozygous deletion of both genes occurred in only 13% of cases. Nine tumors displayed heterogeneous MTAP staining, and the percentage of tumor cells lacking MTAP correlated with molecular detection of MTAP deletion. The findings appeared in Histopathology in 2021.
Absent MTAP staining reliably confirms CDKN2A loss, but retained staining does not exclude the deletion because heterozygous changes often preserve enough protein to produce a positive result.
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