This talk is on peripheral nerve tumors of uncertain behavior, considering the risk of percutaneous image-guided biopsy within a neurosurgical practice. Peripheral nerve sheath tumors are generally divided into two main categories, those that are likely malignant and those that are likely benign. We focused our attention here on tumors that fall in the gray area between those two groups, namely peripheral nerve sheath tumors of uncertain behavior. The decision to biopsy a peripheral nerve sheath tumor is complex and requires balancing multiple clinical as well as tumor-specific factors. Usual care is to proceed with biopsy for tumors believed to be likely malignant because the benefit of tissue diagnosis outweighs the risk of performing a biopsy. This is because tissue diagnosis can change prognosis as well as operative planning for these patients. Conversely, usual care for patients with tumors believed to be likely benign peripheral nerve sheath tumors is to avoid biopsy, and that's because the risk far outweighs the benefit of a tissue diagnosis in patients with presumed benign lesions. We were interested in the decision to biopsy peripheral nerve sheath tumors of uncertain behavior. The role of biopsy in these tumors remains controversial, and the risk as well as the risk-benefit ratio for these tumors is not known. We reviewed notes from a single peripheral nerve surgeon's practice. Patients with percutaneous image-guided biopsy of peripheral nerve sheath tumors were selected for further review, and they were subsequently divided into three groups based on clinical radiologic features. The clinical radiologic features considered were weakness of any degree, pain either moderate or severe, patients with a concerning personal history, including patients with a history of prior malignancy, or patients who described rapid tumor growth. Radiologic concerns included necrosis, irregularity, or invasiveness as seen on MRI scans, hypermetabolic lesions seen on PET imaging, as well as radiologic interpretations stating that the lesion was considered to be a malignant one. The three groups patients were sorted into, likely malignant, these were patients who either had a clinical note documenting that the tumor was believed by the clinician to be malignant, or patients who had weakness and two additional positive clinical radiologic features. Likely benign, this group was made up of patients who had a clinical note documenting the tumor was believed to be benign, or patients who had one positive clinical radiologic feature. Lastly, uncertain tumors, these were patients where a clinical note documented the tumor was indeterminate, or it was uncertain what the tumor's behavior was. Or patients who had two or more positive clinical radiologic features, weakness did not need to be one of these features in our definition. Patient inclusion, there were 159 patients who had image-guided percutaneous biopsies of peripheral nerve sheath tumors at our institution during this time. Eighty-two of these patients were categorized as peripheral nerve sheath tumors of uncertain behavior. Sixty of these patients had been recommended for a biopsy after consultation by a neurosurgeon. The demographics of these patients, 53.9% were female, and the average age was 46 years. Thirty-nine patients had positive clinical features, including 28 patients with pain and 23 patients with weakness. Obviously, there was some overlap between those two groups. Forty-six patients had radiologic features that were concerning for malignancy. However, it's important to note that 31 of the 60 patients ultimately had radiology interpretations stating the lesion was indeterminate or that malignancy could not be ruled out. Risks for the procedures, seven of the 60 patients had complications. This included four patients who had either a misdiagnosis or a non-diagnostic biopsy, three patients who had post-biopsy pain, and one patient who had a transient worsening of pre-existing pre-procedural weakness, and that resolved by their initial follow-up after the biopsy procedure. Looking specifically at the four patients with misdiagnosis or a non-diagnostic biopsy, of those, two had a non-diagnostic biopsy. And at the time of surgery, they were found to have a schwannoma and an angiolarmioma, respectively. The two other patients had a misdiagnosis. Their biopsies were read out as benign peripheral nerve sheath tumors, and at the time of surgical resection, both were found to have malignant peripheral nerve sheath tumors. The benefits to the biopsy, we defined a term that we called HIT rate, which is patients with peripheral nerve sheath tumors of uncertain behavior who underwent biopsy and ultimately had malignant final pathology. These are the patients who are most likely to benefit from having a tissue diagnosis prior to discussion of any surgical intervention and certainly prior to any surgical resection of the lesion. Among the 60 patients recommended for biopsy by a neurosurgeon, 22 of them had malignant final pathology, so a HIT rate of 36.7%. Among the 22 patients referred for biopsy by a non-neurosurgeon, two patients had a malignant final pathology for a HIT rate of 4.55%. There was a statistically significant difference in the HIT rate between the neurosurgeon and non-neurosurgeon referred groups. The risk-benefit ratio for biopsy of peripheral nerve sheath tumors of uncertain behavior, we see this table that covers all three subgroups of peripheral nerve sheath tumors, benign, malignant, and in the middle highlighted tumors of uncertain behavior. So to summarize, the risk of biopsy for patients referred by a neurosurgeon was 11.7%, while the benefit or HIT rate was 36.7%. Among the patients sent for a biopsy by a non-neurosurgeon, the risk was 9.09%, while the benefit or HIT rate was 4.55%. There is no statistically significant difference between the risk in the two groups, but the HIT rate or benefit differed significantly. In conclusion, we found that the risk of biopsy of peripheral nerve sheath tumors of uncertain behavior is relatively low. When misdiagnosis and non-diagnostic biopsies are considered separately, the complication rate drops further to 8.54% overall and 6.67% within the neurosurgeon referred patient group. The risk-benefit ratio is favorable overall, but particularly so in patients who were first evaluated by a neurosurgeon and then referred for biopsy of a peripheral nerve sheath tumor that was determined to be of uncertain character.

percutaneous image-guided biopsies

peripheral nerve sheath tumors

uncertain behavior

neurosurgical practice

risk-benefit ratio