Malignant triton tumor of the common bile duct

Malignant triton tumor (MTT) is a rare subset (5%) of malignant peripheral nerve sheath tumors (MPNSTs), classified as soft-tissue sarcomas. MTT is an orphan disease characterized by rhabdomyoblastic differentiation, therapeutic resistance, and a sinister prognosis. The neoplasms classically arise at the trunk, head and neck region, and extremities. In 50% of the cases, MTT is associated with neurofibromatosis type 1 (NF1), a relatively common autosomal dominant cancer-prone disorder of the central nervous system. Few cases of MTT in the gastrointestinal tract have been published, including esophagus, duodenum, and rectum. In this article, we present what we believe to be the first report of MTT in the common bile duct. A multidisciplinary approach was the key in establishing this particular diagnosis, and workup included endoscopic ultrasound, endoscopic retrograde cholangiopancreatography, pathological staining, and genetic testing. Literature focusing on MTT remains scarce, and patients with MTT are often included with other subtypes in broader studies of MPNST. Therefore, our literature review covers MPNST and focusses on MTT where appropriate. It provides the current understanding of tumor epidemiology, genetics, and diagnostic workup, and discusses therapeutic challenges and future perspectives. Our case report underlines the value of cholangioscopy-guided biopsies, and honoring patient's autonomy in end-of-life setting.