Myoepithelial Carcinoma (MYEC)
Overview
Myoepithelial carcinoma (MEC) is a rare malignant tumor classified under Salivary Gland Cancer in OncoTree (parent: SACA), arising primarily in salivary glands and soft tissue. It is characterized by low tumor mutation burden and oncogenic structural variants (gene fusions, chromoplexy) rather than point mutations in canonical cancer genes, making targeted therapy identification challenging.
Cohorts in the corpus
- stmyec_wcm_2022 — 2 patients with soft tissue MEC profiled by WES and WGS; 12 total tumor samples including primary and metastatic/recurrent lesions PMID:36577525
Recurrent alterations
- SMARCB1 — homozygous deletion with complete protein loss (IHC) in MEC1; loss arising from a biallelic chromoplexy event on Chr 22 PMID:36577525
- NF1 — biallelic loss via chromoplexy in MEC1 PMID:36577525
- EWSR1 — EWSR1(exon 8)::KLF15(exon 2) fusion in MEC2; confirmed by RNA-seq and FISH PMID:36577525
- ELK4 — high-level amplification (>10 copies) via double minute in MEC2 PMID:36577525
- Both cases showed very low TMB (mean 1.35 mutations/Mb, range 0.43–2.98) and COSMIC Signature 3 (HR deficiency-associated), with no detectable somatic HR pathway mutations PMID:36577525
Subtypes
- Soft tissue MEC with SMARCB1 loss shares morphologic and IHC features with malignant rhabdoid tumors; SMARCA2 shows heterogeneous alternating nuclear expression in both subtypes PMID:36577525
- Fusion-driven MEC (EWSR1 rearrangement) versus chromoplexy-driven MEC (SMARCB1/NF1 co-loss) may represent distinct molecular subtypes
Therapeutic landscape
- No actionable therapeutic targets identified in two WGS-profiled MEC cases, including in metastatic/recurrent disease; absence of targetable point mutations underscores reliance on structural variant drivers PMID:36577525
Sources
- PMID:36577525 — Cyrta J et al. “Whole-genome characterization of myoepithelial carcinomas of the soft tissue.” Cold Spring Harbor Mol Case Stud (2022)
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