Malignant Peripheral Nerve Sheath Tumors of the Buttock and Lower Extremity. A Study of 43 Cases

Using strict clinical and pathologic criteria for the inclusion of cases, the authors have reviewed the clinicopathologic features of 43 malignant peripheral nerve sheath tumors of the buttock and extremity seen over a 35-year period. Twenty-three (53%) of the patients had neurofibromatosis (VRN), whereas 20 (47%) did not. Fifty-one percent of the patients were women. The mean age at presentation was 36 years for patients with VRN and 44 years for patients without VRN. A nerve of origin was identified for 72% of the cases and an associated neurofibroma for 44% (65% with VRN and 20% without VRN). The mean greatest dimension of the tumors was 12.3 cm, and this did not differ significantly between the two groups. The predominant histologic pattern in 86% of the tumors was that of tightly packed spindle cells in an interlacing and woven pattern; heterologous sarcomatous elements were noticed in 12% of the cases. Surgical resection was the main modality of treatment for all patients; 65% also received adjuvant therapy. Follow-up evaluation was done in every case. An unexpected finding was the absence of a significant difference in survival rates between patients with and without VRN. Overall, 63% of the patients died of tumor: 65% of the patients with VRN and 60% of the patients without VRN. Large tumor size and high mitotic rate (greater than 20 per 10 high-power fields) portended a poor prognosis, as did the need for resection by amputation. Adjuvant radiation therapy and chemotherapy did not affect survival rates.