Rationale: Malignant peripheral nerve sheath tumor occurring in the context of neurofibromatosis type I (NF1) is relatively rare. Herein, we report a case of NF1 with malignant peripheral nerve sheath tumor in the upper arm.
Patient concerns: A 24-year-old man presented with a mass in the medial part of the left upper arm that had been present for more than 20 years. In the previous 1 year prior to admission, the mass had grown significantly. Physical examination showed cafe-au-lait spots of variable sizes throughout the body and multiple masses in the medial part of the left upper arm. Three months later after the resection of the masses, the patient was readmitted to our department due to tumor recurrence. Two months after the extended resection, in situ recurrence of the tumor was noted again. Four months after the operation and the administration of radiotherapy, a mass was found in the outside of the left upper arm.
Diagnosis: Immunohistochemical staining showed the masses were positivity for vimentin, CD34, and S100; the tumor cells were negative for PGP9.5, CD57, EMA, and SMA. The Ki-67 labeling index was approximately 40%. A diagnosis of malignant peripheral nerve sheath tumor was made.
Interventions: Surgical resection was performed for both the primary tumors and the 2 subsequent recurrence tumors. The patient underwent radiotherapy with 60 Gy in 30 fractions after the third operation. Four months after the administration of radiotherapy, the patient underwent tumorectomy of a mass in the outside of the left upper arm.
Outcomes: During the 4-month follow-up after the fourth operation, the patient's condition was stable.
Lessons: Malignant peripheral nerve sheath tumor in NF1 is an exceedingly rare entity that poses a great diagnostic challenge. High-frequency ultrasound can support the diagnosis.