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Washington University Experience | NEOPLASMS - CRANIAL AND PARASPINAL NERVEs | Malignant Peripheral Nerve Sheath Tumor (MPNST) | 17E MPNST, low grade (Case 17) p53 1.jpg
There is strong nuclear p53 staining in rare tumor cells in the hypercellular regions only. ---- Comment: FISH studies were performed to rule out EGFR amplification and deletions of p16 and NF2 as these genetic alterations are more often associated with MPNST. However, in the current case normal copies of chromosome 9 and polysomies (gains) of chromosomes 7 and 22 were observed. Although the latter finding is non-specific, such chromosomal gains are more common in MPNSTs than in neurofibromas. ---- Comment: The tumor predominantly has a diffuse neurofibroma phenotype but in the hypercellular areas, the morphologic, immunohistochemical, and genetic features are most consistent with low-grade malignant peripheral nerve sheath tumor (MPNST). Using the FNCLCC sarcoma grading scheme, this tumor would be scored as 2 for differentiation, 1 for mitosis count, and 0 for necrosis, yielding a total score of 3 and an overall grade of 1 (of 3). The small tumor size, low histologic grade, and negative surgical margins all suggest a more favorable prognosis.
