METHODOLOGY: A total of 59 benign and malignant spindle cell tumours (18 MPNST and 41 of its histologic mimickers which included 10 schwannoma, 13 neurofibroma, 4 synovial sarcoma, 3 fibrosarcoma, 2 gastrointestinal stromal tumour (GIST), 4 leiomyosarcoma, 1 spindle cell liposarcoma, 1 solitary fibrous tumour, 2 low grade fibromyxoid sarcoma and 1 unclassified spindle cell sarcoma), diagnosed from January 1998 to April 2018 in Hospital Universiti Sains Malaysia (HUSM) were tested for H3K27me3 by IHC. The MPNST histological grade was assessed based on the French Fe'de' ration Nationale des Centres de LutteContre le Cancer (FNCLCC) for 3 tiers system (low grade, intermediate grade and high grade). The clinicopathological data were retrieved from the patients' record.
RESULTS: A total of 61.1% (11/18 MPNST) showed loss of H3K27me3 expression which is statistically significant as compared to its histologic mimics (p<0.001). Similar findings (p=0.026) were also observed in high grade MPNST (81.8%), intermediate grade MPNST (100%) and 0% in low grade MPNST.
CONCLUSION: H3K27me3, combined with other panel of markers, is useful in MPNST diagnosis to differentiate it from the histological mimickers.