Metastatic malignant peripheral sheath tumor

Case contributed by Alba Antón Jiménez


Instability and aphasia.

Patient Data

Age: 45 years
Gender: Female

Brain CT performed at the time of admission showed a large left frontal lesion producig mass effect with midline shift, partial compression of ventricles and signs of uncal and subfalcine herniation. It had heterogeneous enhancement with areas of inner necrosis.

Brain MRI.


Brain MRI confirmed the presence of an intra-axial lesion with well-defined margins that had heterogeneous contrast enhancement with a central necrotic component. The voluminous lesion and its perilesional edema produced a significant mass effect.

The peripheral solid component of the lesion had diffusion restriction and an increase in cerebral blood volume on perfusion-weighted images. Susceptibility-weighted images demonstrated blood vessels and hemorrhagic foci inside the lesion.

Chest X-ray.


A previous chest X-ray was a clue for the final diagnosis. It revealed a voluminous mass occupying the left hemithorax and producing mediastinal shift that corresponded to a malignant peripheral nerve sheath tumor of the thorax.

Gross pathology: brain lesion


Histology study (surgical specimen) showed an uniloculated well-circumscribed and encapsulated mass with highly vascularization and inner necrosis.

Histology: brain lesion


Hystology study (microscopy) established the diagnosis of metastatic malignant peripheral nerve sheath tumor. 

Hematoxylin and eosin staining revealed a cluster of epitheloid cells in a myxoid/hyalinized stroma.

There is loss of Histone H3K27 trimethylation (specific finding of high-grade malignant peripheral nerve sheath tumor) and S100 staining in trapped astrocytes. 

Case Discussion

Patient with a previous history of Neurofibromatosis type 1 (NF 1) and malignant tumor of the peripheral nerve sheath in the mediastinum. The patient developed costovertebral and pulmonary metastasis that were surgically removed. After that, the patient presented to the emergency department with instability and aphasia.

Malignant Peripheral Nerve Sheath Tumors (MPNST) are uncommon tumors representing 5% of all soft tissue sarcomas. The majority are associated with Neurofibromatosis type 1 (NF 1) 1.

The most common CNS tumors encountered in NF 1 are optic pathway and brainstem low-grade gliomas. However, young adults with NF 1 are also prone to develop malignant gliomas or glioblastomas (10 to 50-fold increased risk). For this reason, adults with NF1 who present with signs of increased intracranial pressure or neurologic deficits should be promptly evaluated with neuroimaging studies. Unfortunately, the prognosis for NF 1-associated malignant glioma is dismal.

In our case, brain CT and MRI showed a single large intra-axial mass in the left frontal lobe, with well-defined margins, central cystic-necrotic changes and severe mass effect.

Our differential diagnoses consisted of:

  • Atypical meningioma. Despite the lesion seemed to contact the falx cerebri on the CT, brain MRI clealy demonstrated its intraaxial nature, excluding this diagnosis. 
  • Malignant glioma or glioblastoma. A glioblastoma was suspected due to the presence of an enhancing mass with central necrosis, increase cerebral blood volume, internal blood vessels and foci of hemorrhage. However, infiltrative margins typical of high-grade gliomas were not seen in our case.

Histological analysis of the brain lesion after complete surgical resection established the diagnosis of MPNST metastasis.  Two months after surgery, the patient is asymptomatic and under chemotherapy treatment.

MPNST metastatic disease is common, but brain is an extraordinary atypical metastatic location, with only 21 cases reported since 1963 1-4.

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