MiT Fusions, TSC1–TSC2 Divergence, and Stem-like Programs Reveal Distinct Origins and Vulnerabilities in PEComa [scRNA-seq]

Here we perform comprehensive multi-omic profiling of an unselected PEComa cohort. We identify frequent MITF rearrangements involving actin gene partners (ACTA2, ACTG1 and ACTB).

Anatomical stratification reveals cyclin-dependent kinase module mutations in gynecologic tumors, whereas soft tissue, gastrointestinal, and pelvic tumors lacked mTOR pathway alterations but are enriched for TFE3/MITF rearrangements. Transcriptomic analysis defines four subtypes with distinct lineage programs—melanocytic, mesenchymal, or adipogenic—as well as unique mutational patterns and clinical behaviors. Notably, an aggressive stem-like subtype enriched for TP53/RB1 mutations exhibits high proliferation, activation of embryonic and Hedgehog signaling, immune infiltration, and resistance to mTOR inhibitors, but potential responsiveness to immunotherapy.