Enrico Martin

97 Oncological treatment considerations treating STS and NF1 both recommend performing MRI imaging and core needle biopsies to obtain a histopathological diagnosis. 21–23 Although radiological features and presenting symptoms are not specific for malignancy, some general indications should make surgeons aware of a potential malignancy. Irregular shape and border, lobed aspect, cystic changes, heterogeneous structure, absence of a target sign (distinctive for neurofibromas), and peritumoral edema on MRI may indicate malignant transformation in MPNSTs. 8,9,24 Tumors larger than 5cm or deep to the fascia definitely justify imaging and biopsy. 21,23 However, preoperative identification of malignancy in NF1 patients is particularly difficult, as atypical and plexiform neurofibromas can present similarly to MPNSTs. Recent research has shown that FDG-PET scans can be helpful in distinguishing malignant from benign lesions, differentiating MPNSTs from neurofibromas with a 80% specificity and almost 100% sensitivity, 25,26 which is why an NF1 consensus does recommend performing it. 22 Others have shown that diffusion-weighted imaging sequences in MRI can differentiate malignancy with 100% specificity, however these techniques are not standard of care in many centers. 24 As neurosurgeons see neurofibromas commonly, it may explain the high proportion of neurosurgical respondents performing FDG-PET scans preoperatively. While surgical oncologists more commonly adhere to guidelines recommending core needle biopsies as preferred biopsy, 21–23 a larger proportion in other subspecialties favor open biopsies as well. If an open biopsy were to be considered, ideally the same surgeon performing the tumor excision should execute the biopsy as risk of tumor spread is substantially higher. 21–23 Excisional biopsy can also be considered for superficial tumors <3cm, as this may be most conventional. 21,22 Differences in preferred biopsy technique between subspecialties may therefore possibly be explained by specialty bias. Fine needle aspirations are discouraged in MPNSTs as they have a high risk for uncertain diagnoses because of small specimen sizes. 21–23,27 Surgical treatment in MPNST Complete surgical excision with wide margins is the routine treatment of choice. 4,10,21,22 Nonetheless, even when obtaining R0 margins, MPNSTs can recur. 2–4,15,16 Some authors even propose that fresh frozen coupes are necessary intraoperatively. 2,3,28 There is a possibility that as MPNSTs have their perineural origin, skip lesions may be present along the nerve of origin. 28 Respondents to this survey also felt that resecting a longer course of the nerve may therefore be beneficial, encouraging future studies to evaluate this in depth. And while R1 resections are associated with a higher likelihood of recurrence, several large MPNST series have not shown that R1 resections are associated with worse survival compared to R0 resections. 4,6,10 This indicates a potential role for operating with closer margins in order to preserve function without altering a patient’s prognosis. 29 For instance tumors in the brachial plexus may be adequately treated with epineural dissection and nerve reconstructions avoiding the need for a forequarter amputation. 30 Contrarily, 42% of respondents to this survey would never perform less extensive resections even if free surgical margins were not 5