Greetings, everyone. My name is Dr. Roberto Perez-Román. I am a fourth-year resident at the University of Miami Neurosurgery Program, and I'll be talking about our project, the risk of peripheral nerve tumor biopsy in suspected benign etiologies. There are no disclosures related to this talk. Benign peripheral nerve sheath tumors represent approximately 10% of all benign soft tissue neoplasms, and they are basically neoplastic proliferations with Schwann cell differentiation. There are two distinct types of benign peripheral nerve sheath tumors, which are schwannomas and neurofibromas, along with their variants. It is important to point out that there are other benign entities that can involve the nerve secondarily, which include lipomas, ganglion cysts, traumatic neuromas, among others. Malignant peripheral nerve sheath tumors can be distinguished in some cases from benign lesions on both clinical and radiological grounds. If you have a patient that presents with a slow-growing painful mass with no motor deficit, you will start to suspect a benign lesion, versus if you have a patient that presents with a rapid-growing lesion, severe pain, and progressive motor deficit, this sounds of a lesion with a more malignant nature. Also, in patients with neurofibromatosis type 1, if they develop new, worsening, or persistent pain in a known neurofibroma, you suspect a malignant transformation. On imaging, benign lesions in general are well-demarcated. They are smaller. They can present with a target sign on T2 sequences, and they have no diffusion restriction. On the other hand, malignant lesions tend to be more invasive. They present usually with a size that is larger than 5 centimeters, and they restrict on diffusion. Adjunct imaging, like PET-CT, has been shown in the literature to be very helpful in differentiating malignant from benign lesions. Several studies have shown that a SUV max of greater than 5.5 yields a high sensitivity and specificity to differentiate malignant from benign lesions. It is very common for radiological reports to recommend obtaining a biopsy to confirm diagnosis in these lesions, and we as neurosurgeons should be prepared to guide these patients to the correct treatment modality. Biopsy can be performed either percutaneously with ultrasound guidance or open. It is very important to notice that on malignant lesions, the biopsy represents the correct course of action because if they undergo an inappropriate intertrapsular tumor resection, there is a high risk of incomplete resection, tumor seeding, and fatal tumor recurrence. But in benign lesions, peripheral nerves are at risk because of potential injury to functional fascicles. Relying on ultrasound alone to identify fascicles around or within the nerve tumor requires resolution down to the submillimeter level, which is very hard to obtain with ultrasound. Here we have an illustration showing how a percutaneous biopsy can injure a nerve fascicle that is in close proximity to a benign peripheral nerve sheath tumor. With this project, we try to evaluate the neurological risk of preoperative biopsy in benign peripheral nerve sheath tumors. This study comprised of a retrospective review of the Singer Surgeon Series from 1997 to 2019 from a prospectively collected database of all tumors that underwent surgical resection. A detailed exam was obtained pre- and post-surgery at two weeks and three months follow-up. There was a total of 225 cases, but after malignant and lesions associated with the cranium or spine were excluded, 151 cases were studied. The majority of them were schwannomas, but neurofibromas, lipomas, and other closely associated lesions were studied. Here is a table showing the demographics of all the tumors that were studied. 35 cases had biopsy prior to surgery, 60% of them had an open procedure, while 40% had a percutaneous technique employed. About 43% experienced new neurological deficits immediately after biopsy. 11 developed new significant neuropathic pain, 2 had new numbness, while another pair had new weakness. Of the 15 biopsy cases, 8 were non-diagnostic. Interesting, there was no difference in development of neurological deficit in respect to technique used. Following resection itself of these benign tumors, around 72% of the patients did not have any change in their neurological status. In regards to follow-up, 100% of the patients were seen at 2 weeks, and around 82% of the patients were seen at 3 months with a detailed neurological exam. Patients that had a history of biopsy, 60% of them presented in the postoperative period with new deficits, and these are independent of the deficits caused by the biopsy itself. Versus only 19% of the patients with new deficits and those who did not undergo a preoperative biopsy. So basically, here's a table showing the increased neurological deficit at definite surgery after follow-up. So prosurgical biopsy increased the overall risk of developing any new motor, sensory, or neuropathic symptoms with an ALT ratio of 6.4. When deficits were analyzed according to the subtype of the deficit, it shows that the ALT ratio for motor deficit was higher at 7.03, followed by neuropathic pain, which had an ALT ratio of 4.58. And there was an ALT ratio of developing sensory deficit of 2.57, but it was not significant. After an univariate logistic regression analysis of any composite and individual neurological deficit in regards to age, sex, tumor pathology, and preoperative biopsy showed biopsy was only significantly associated with the occurrence of any postoperative deficit and neuropathic pain. Occurrences of sensory deficit were less likely to develop in a male patient with an odds ratio of 0.25. And there was an odds of a motor deficit increase with each year above the sample mean with an odds ratio of 1.03 per year. Here is an example from our series. This is a 61-year-old male patient with a three-year history of right leg pain with no motor deficit. He had imaging done to show an enhancing lesion on the right sciatic nerve. He underwent a percutaneous biopsy at an outside facility. Initial pathology was a lipoma, but the patient developed new severe neuropathic pain after that procedure. He was referred to our clinic and he underwent surgical resection. And we can see intraoperative picture on letter C and letter D. He underwent a successful complete resection of this tumor. Letter F, we can see the postoperative MRI. And on letter E, we can see the final pathology that showed compact spindle and Tony A areas alternating with loose hypocellulite and microcystic and Tony B regions that obviously are characteristic of shonoma, which that was the diagnosis in this case. In conclusion, we suspect that preoperative biopsy may cause inflammation and scarring within the lesion obscuring the planes between normal fascicles and the tumor, making definite surgery more difficult. It's important to point out that biopsy remains a useful tool, but must be used with caution. And in cases of suspected benign pathology, poses an unacceptably high risk for the patient. Poses an unacceptably high risk of developing neurological deficits. Tumors suspected to originate from peripheral nerves should be referred to a specialist early to try to mitigate the negative effects. Thank you for your attention. Hope you learned something from this talk.

Dr. Roberto Perez-Román

University of Miami Neurosurgery Program

peripheral nerve tumor biopsy

benign soft tissue neoplasms

neurological deficits