Slow Spinal Cord Compression Inducing by Malignant Peripheral Nerve Sheath Tumors in Cotonou

MPNST is a very uncommon malignant type of neoplasm. It is often associated with neurofibromatosis type 1 (von Recklinghausen disease). It involves large anatomical regions, and thus takes on varied clinical presentations. However, bone location of MPNST, particularly in the spinal canal has been poorly described in the literature. We hereby report the case of a 29-year old young man with MPNST in the spinal canal. He presented a slow spinal cord compression confirmed by spinal MRI. MPNST was revealed through histologic and immune histochemical features after tumor resection.


Introduction
Malign peripheral Nerve Sheath Tumors (MPNST), as defined per the 2013 WHO classification, are malignant tumors arising from a peripheral nerve, or from a pre-existing benign nerve sheath tumor. They can also occur in a patient with neurofibromatosis (NF-1).

Observation
Mr. D. M., aged 29, with no specific medical prior history, was admitted with gradual onset of motor deficit in the lower limbs. Symptoms had been developing for 8 weeks, including back pain upon coughing that radiated around left side of the body to the middle of the chest, then painless intermittent claudication occurred. A week before he was admitted, he experienced motor decline in the pelvic limbs with acute urinary retention requiring consultation in the emergency department. He had neither fever nor cough, and presented no signs of trauma. His examination revealed a generally altered condition with WHO performance indicator estimated at 3/4. The neurological examination highlighted spastic paraparesia with muscle strength rated at 3/5 and a bilateral Babinski sign. Sensitivity disorders such as hypoesthesia upon protopathic touch and the rmalgesic type of disorders were found with sensitivity up to dermatome T2. He had sharp pain from T2 to T5. Skin smear examination revealed neither brown skin patches nor neurofibromas. Blood test (CBC Normal, CRP negative) and tuberculin skin test were negative. Spinal MRI ( Figure 1 and Figure 2) showed a 5 cm tumor mass, low signal intensity on T1 at the level of T2 thoracic vertebra and high signal intensity on T2 with bone marrow involvement. Tumor-induced slow spinal cord compression was diagnosed and laminectomy was taken with tumor resection. The pathological examination of the resected specimen was carried out in Europe and the results were sent back 6 weeks later. Proliferation of monomorphic malignant spindle cell tumors was evidenced, with predominance of hemangiopericytoma structure ( Figure 3). The morphological and phenotypic profile of this tumor suggested a Malignant Peripheral Nerve Sheath Tumor (MPNST) with glandular differentiation. Extension work up specifically thoracic-abdominal-pelvic CT scan revealed no particularities. The patient passed away with respiratory distress, 1 month after he was discharged, and before getting the histological and immunohistochemical results.

Discussion
MPNST is a nervous system tumor which develops to the detriment of the nerve sheath, resulting from the impairment of derived neural crest and ectoderm cells [6]. It is a rare tumor with an incidence of 0.001% among the general population and 5% -10% among NF1 patients [7]. It is much higher among NF1 patients because the NF1 gene located on the long arm of chromosome 17 and encoding the neurofibromin protein plays a role in MPNST genesis [8]. MPNST is asso-  [5]. Plexus and large nerves are the preferential locations. NF1 associated with intraosseous MPNST is less prevalent [9] than with soft tissue injuries [17] and thus the absence of neurofibromatosis type 1 in the case of our patient. In fact, neurofibromatosis type 1 diagnosis is clinical in most cases [18].
There is no typical imaging of MPNST [15]. Our patient's MRI helped to deter- MPNST definitive diagnosis is confirmed through histology [7]. In our case, a biopsy was carried out along with histology which was sent in Europe, and con- out. In all cases, MPNST prognosis is also poor [20]- [28]. The 5-year survival rate is 20% to 50% [29]. The overall development depends on the histological grade of the tumor, its size, location, whether or not it is associated with NF1, and finally the possibility and quality of primary surgery [30]. The risk of local recurrence is 40% to 65% [31]. Metastases are blood-borne or follow the pathway of nerve sheaths. Distant metastases are located in the lungs, liver and bones. They appear in an average period of two years. Such a period is shorter when there is NF1 [12]- [32].

Conclusion
MPNST is a rare and dreadful life-threatening disease. It presents a clinical polymorphism depending on its specific anatomic site, which can turn out to be slow spinal cord compression. But this is uncommon as MPNST has low osseous tropism. MRI remains the preferred examination for diagnosing spinal cord compression but not for MPNST. The definitive diagnosis is based on histology. In sub-Saharan Africa, the difficulties in diagnosing and the challenging post-surgery follow-up of this condition makes this tumor a life-threatening disease.