Malignant Peripheral Nerve Sheath Tumor (MPNST) Arising from Orbital Plexiform Neurofibroma in a Small Child With Neurofibromatosis Type 1.

Background/aim: Neurofibromatosis type 1 (NF1) is an autosomal dominant hereditary tumor predisposition syndrome. In approximately 30% of cases, plexiform neurofibromas (PNFs) are identified, which are precursor lesions for malignant peripheral nerve sheath tumors (MPNSTs). MPNST is a major cause of the reduced life expectancy of NF1 patients.

Case Report: The patient, a two-year-old at the time of surgical treatment, had been diagnosed with an orbital nerve sheath tumor causing lid swelling and ptosis since birth. The tumor showed disproportionately rapid growth, leading to increasing functional (mechanical) restrictions in lid elevation. Surgical exploration of the orbit indicated a PNF with areas of a MPNST. Two months later, a new biopsy confirmed the MPNST. The tumor was treated with multimodal chemotherapy. After completion of chemotherapy, orbital exenteration was performed. The tissue specimens only comprised tissue of a benign PNF. However, within six months, the patient developed an intracranial recurrence and died from a rapidly growing intracerebral tumor fraction, which histologically proved to be a MPNST.

Conclusion: Orbital PNF is a rare and characteristic manifestation of facial NF1. Typically, tumors in this localization are associated with severe functional disabilities and aesthetic disfigurement, resulting from invasive tumor growth and skeletal deformities. Histological classification of the tumors may be challenging due to varying histological differentiation in different tumor locations. Thus, early diagnosis with representative tumor sampling and complete histological work-up of the specimen together with multimodal therapy are essential prerequisites to overcome the poor prognosis of these tumors.