gms | German Medical Science

Objectives: The Swiss national sarcoma advisory board (SNSAB) recommends biopsy in case of subfascial lesion, superficial lesion > 3-5cm and lesions suspicion for malignancy in T1 or T2 weighted MRI. Recently false positive biopsy results and the risk of possible nerve damage by performing biopsy of nerve related tumors (NRT) question this approach. Our objective was to evaluate the relative prevalence of malignant NRT and to determine the rate of accurate diagnosis as well as complications in performed biopsies.

Method: We reviewed patient charts with surgical treatment for NRT between January 2007 and February 2018. All patients had preoperative MRI and/or sonography. The number of preoperative performed biopsies was recorded. Excision of all NRT was performed. Suspected MRI findings as well as biopsy findings were compared with the definite histopathological report (DHR).

Results: In the 11 year period we identified 66 patients with 71 NRT. 36 (55%) were female, the median age was 53 (IQR 41-64). In DHR 8% of the tumors were malignant, 76% were diagnosed as schwannomas. Of 60 (91%) performed MRI, 47 (78%) were suspect for a benign and 7 (12%) for a malignant finding. 6 (10%) images were non distinctive. 2 (4%) of the MRI suspected benign tumors showed malignancy and 5 (71%) of the suspected malignant tumors showed benign findings in DHR. In 16 (24%) cases a preoperative biopsy was performed. 8 biopsies diagnosed a benign and 2 a malignant tumor. 6 biopsies were non distinctive (38%). In 56% cases of taken biopsies the finding was confirmed by the DHR. None (0%) of the diagnosed benign biopsy but both (100%) of the malignant biopsy turned out to be misdiagnosed compared with the DHR. Against the SNSAB guidelines we performed a marginal resection to preserve the brachial plexus in this patient. 2 (13%) patients suffered a nerve lesion while performing biopsy. In both cases DHR showed a benign tumor.

Conclusion: 8% of suspected NRT were malignant. Suspected MRI diagnosis was confirmed in 77% but the diagnosis of biopsy could only be confirmed in 56% of cases. Our cohort showed no false negative but 100% false positive biopsy results. This misdiagnosis can lead to severe morbidity when treated with wide resection according the SNSAB. 2 patients showed a nerve lesion after biopsy. These findings suggest excisional but no needle or incisional biopsy in NRT if clear relation to the involved nerve by sonography or MRI can be demonstrated.