Optical Coherence Tomography Angiography-Navigated Laser Photocoagulation of Retinal Hemangioblastomas in Patients With von Hippel-Lindau Disease.

Purpose: To describe optical coherence tomography angiography (OCTA)-guided navigated laser photocoagulation (LP) using the Navilas Laser System for treating retinal hemangioblastomas (RHs) associated with von Hippel-Lindau disease (VHLD). Methods: Patients with VHLD were screened using ophthalmoscopy and widefield OCTA. Detected RHs were classified with regard to tumor morphology (endophytic, sessile, exophytic, recurrent) and size. Then, 6 × 6- or 3 × 3-mm2 en face OCTA scans of the RHs were uploaded to the Navilas system, generating a merged image combining the scan and Navilas fundus photography. LP was planned by placing laser spots in the OCTA scan and executed with the Navilas system. Treatment efficacy was assessed by conducting OCTA scans immediately after LP and at follow-up visits. Results: Fifteen RHs were detected in 10 patients (median, one RH; range, one to four). Twelve RHs were treatment naive (exophytic [3], sessile [3], and endophytic [6]), and there were three recurrent RHs in pretreated areas. Total applied energy per tumor correlated with tumor size (P < 0.001). After a mean first follow-up of 3.6 ± 1.5 months (range, 0.9-5.3), nine RHs exhibited complete regression (60%), five partial regression (33.3%), and one no regression (6.7%). No correlation between tumor morphology and treatment success was observed (P = 0.32). However, a correlation between treatment success and tumor size trended toward significance (P = 0.08), with a 100% success rate observed for small RHs. Conclusions: OCTA-guided LP via the Navilas Laser System is a promising technique, especially beneficial for targeting small RHs. Combining OCTA and ophthalmoscopy improves tumor detection, underscoring the utility of this approach. Translational Relevance: OCTA-guided LP enables highly precise and safe treatment of early-stage RHs, minimizing possible complications caused by LP or the tumor itself.

Characterization of spinal hemangioblastomas in patients with and without von Hippel-Lindau, and YAP expression.

INTRODUCTION: Hemangioblastoma (HB) is a benign tumor of the central nervous system, associated with von Hippel-Lindau disease (VHL), or sporadic. The aim of this study was to compare and examine the clinical-pathological profile of patients with spinal hemangioblastoma and YAP expression. METHODS: A retrospective, descriptive, comparative study. All patients who underwent surgery for spinal HB between 2016 and 2023 were included. Clinical and radiological data were collected and analyzed. An immunohistochemistry panel including NeuN, neurofilaments (NF), and YAP-1, was performed. RESULTS: Nine patients were studied, six women and three men. Four patients had previously diagnosed VHL. The tumor location included: four cervical (44.44%), two thoracic (22.22%), two pontine with cervical extension (22.22%) and one patient with two lesions, one cervical and one thoracic (11.11%). Non-significant clinical differences were identified between VHL and sporadic patients. Imaging evidenced seven extramedullary and three intramedullary tumors. Histologically, intra-tumoral and perivascular axonal tracts were observed in all cases. One third of the tumors (two with VHL and one sporadic) presented extramedullary hematopoiesis. Seven cases (77.8%) expressed nuclear YAP (three with VHL and four sporadic HBs). The surgical outcome was good and only one patient with VHL undergoing subtotal resection had recurrence. CONCLUSIONS: Spinal HBs can be associated with VHL or be sporadic. To the best of our knowledge, this is the first study to describe YAP expression in HB. It is important to investigate the involvement of the Hippo pathway in HBs as a possible therapeutic target.

Expression of somatostatin receptors in hemangioblastomas associated with von Hippel-Lindau disease as a novel diagnostic, therapeutic, and follow-up opportunity: A case report and literature review.

Hemangioblastomas associated with von Hippel-Lindau (VHL) disease are frequently multiple and recur during prolonged follow-up. Currently, no systemic treatment is available for these tumors. Recent studies have shown the expression of somatostatin receptors in these types of hemangioblastomas. Notably, increased somatostatin receptor expression in a tumor, as determined by peptide-receptor radionuclide imaging, is a predictive factor of response to treatment with somatostatin analogs and peptide-receptor radionuclide therapy. The aim of this study was to describe the case of a patient with increased expression of somatostatin receptors in a suprasellar hemangioblastoma associated with VHL disease and conduct a literature review on somatostatin receptor expression in patients with VHL-associated hemangioblastomas. We describe herein the case of a 51-year-old man with VHL disease who had a suprasellar hemangioblastoma detected on magnetic resonance imaging. Peptide-receptor radionuclide imaging using gallium-68-DOTATOC (68Ga-DOTATOC) identified increased expression of somatostatin receptors in the suprasellar hemangioblastoma, along with multiple pancreatic neuroendocrine tumors and bilateral pheochromocytomas. The patient was treated for 1 year with lanreotide, a somatostatin analog. A repeat 68Ga-DOTATOC 1 year after starting lanreotide revealed decreased radiotracer uptake by the hemangioblastoma, consistent with a metabolic response. The presence of somatostatin receptors in hemangioblastomas associated with VHL disease is a novel finding. The decreased expression of these receptors after treatment with a somatostatin analog, as described in the present case, positions the somatostatin receptor as a new target for novel diagnostic, therapeutic, and follow-up opportunities in patients with VHL disease.

A Cerebellar Tumor-to-Tumor Metastasis in a Patient With Von Hippel-Lindau Disease.

Tumor-to-tumor metastasis in the central nerve system is uncommon in our routine practice. Most reports include metastatic breast cancer into meningioma. Here we report a metastatic clear cell renal cell carcinoma (ccRCC) into a cerebellar hemangioblastoma in a patient with von Hippel-Lindau (VHL) disease. Imaging cannot distinguish metastatic ccRCC from primary cerebellar hemangioblastoma. Immuno-molecular studies are proven to be diagnostic. We also reviewed previously documented tumor-to-tumor metastasis of ccRCC to cerebellar hemangioblastoma in VHL disease. Lastly, we discussed potential mechanisms involved in the metastasis of ccRCC to hemangioblastoma in the cerebellum in patients with VHL.

Longitudinal Pulse-Synchronous Bouncing During Catheter Angiography-A Phenomenon Specific to Spinal Hemangioblastomas.

BACKGROUND: Spinal hemangioblastomas are often evaluated with catheter angiography for both workup and treatment planning. We report a unique longitudinal pulse-synchronous bouncing phenomenon observed during their angiographic evaluation and consider the association of pulse-synchronous bouncing with syringomyelia, another pathologic feature associated with hemangioblastomas. METHODS: Preoperative spinal angiograms and associated magnetic resonance imagings (MRIs) obtained over a 16-year period at a single institution were retrospectively evaluated. Magnetic resonance imaging (MRI) parameters included lesion and syrinx location and size. Angiograms were evaluated for bouncing phenomena. Student's t-test and Chi square test compared characteristics between groups. Linear regression analyses evaluated maximum amplitude of dynamic motion and any associated syrinx. RESULTS: Nineteen hemangioblastoma patients had preoperative angiograms available for review. Eight exhibited bouncing behavior. Between the dynamic and nondynamic cohorts, there was no difference in presence or volume of syrinxes. Lesions in the dynamic cohort trended towards a cervical location (75% vs. 36.3%, P = 0.10). No significant correlation was found between bouncing amplitude and syrinx size (R2 = 0.023). Dural contact may be related to this dynamic behavior since other high-flow lesions like AVMs do not demonstrate this phenomenon, and AVMs are pial-based and more likely to contact stationary dura. Here, there were fewer lesions abutting the thecal sac in the dynamic cohort (50% vs. 81.8%, P = 0.14). CONCLUSIONS: Though no significant relationship was established between this bouncing behavior and syrinx formation, noted trends included a greater range of motion for cervical lesions and limited motion in tumors abutting the thecal sac.

Screening and surveillance recommendations for central nervous system hemangioblastomas in pediatric patients with Von Hippel-Lindau disease.

PURPOSE: Von Hippel-Lindau (VHL) disease is an autosomal-dominantly inherited tumor predisposition syndrome. One of the most common tumors are central nervous system (CNS) hemangioblastomas. Recommendations on the initiation and continuation of the screening and surveillance program for CNS tumors in pediatric VHL patients are based on small case series and thus low evidence level. To derive more robust screening recommendations, we report on the largest monocentric pediatric cohort of VHL patients. METHODS: We performed a retrospective analysis on a pediatric cohort of 99 VHL patients consulted at our VHL center from 1992 to 2023. Clinical, surgical, genetic, and imaging data were collected and statistically analyzed. RESULTS: 42 patients (50% male) developed CNS hemangioblastomas, of whom 18 patients (56% male) underwent hemangioblastoma surgery (mean age at first surgery: 14.9 ± 1.9 years; range 10.2-17). The first asymptomatic patient was operated on at the age of 13.2 years due to tumor progress. Truncating VHL mutation carriers had a significantly higher manifestation rate (HR = 3.7, 95% CI: 1.9-7.4, p < 0.0001) and surgery rate (HR = 3.3, 95% CI: 1.2-8.9, p = 0.02) compared with missense mutation carriers. CONCLUSION: We recommend starting MRI imaging at the age of 12 years with examination intervals every (1-) 2 years depending on CNS involvement. Special attention should be paid to patients with truncating variants. Affected families should be educated regularly on potential tumor-associated symptoms to enable timely MRI imaging and eventually intervention, as CNS hemangioblastoma may develop before screening begins. GERMAN CLINICAL TRIALS REGISTER REGISTRATION NUMBER: DRKS00029553, date of registration 08/16/2022, retrospectively registered.

Predictive Factors of Long-Term Neurologic Outcome and Progression-Free Survival in Intramedullary Spinal Cord Tumors: A 10-year Single-Center Cohort Study and Review of the Literature.

BACKGROUND: Intramedullary spinal cord tumors (IMSCTs) are a rare subgroup of neoplasms, encompassing both benign, slow-growing masses, and malignant lesions; radical surgical excision represents the cornerstone of treatment for such pathologies regardless of histopathology, which, on the other hand, is a known predictor of survival and neurologic outcome postsurgery. The present study aims to investigate the relevance of other factors in predicting survival and long-term functional outcomes. METHODS: We conducted a review of current literature on functional outcomes of IMSCTs, as well as a 10-years prospective analysis of a wide cohort of patients with diagnosis of IMSCTs who underwent surgical resection at our institution. RESULTS: Our series encompasses 60 patients with IMSCTS, among which 36 ependymomas, 6 cavernous angiomas, 5 hemangioblastomas, 6 WHO Grade I-IV astrocytomas, 3 intramedullary spinal metastases and 4 miscellaneous tumors. GTR was achieved in 76,67% of patients, with high preoperative McCormick grade, syringomyelia and changes at neurophysiologic monitoring being the strongest predictors at multivariate analysis (P = 0.0027, P = 0.0017 and P = 0.001 respectively). CONCLUSIONS: Consistently with literature, preoperative neurologic function is the most important factor predicting long-term functional outcome (0.17, CI 0.069-0.57 with P = 0.0018), advocating for early surgery in the management of IMSCTs, whereas late complications such as myelopathy and neuropathic pain were present regardless of preoperative function.

Hemangioblastoma: An Uncommon Cause of Polycythemia in a Child.

Polycythemia is a rare condition in children. Myeloproliferative neoplasms, including polycythemia vera although rare, is an important cause of childhood primary polycythemia. Secondary polycythemia is more common in children due to conditions causing hypoxia or due to pathologic erythropoietin production in malignancies like renal cell carcinoma, Wilms tumor or Hepatocellular carcinoma. Central nervous system hemangioblastoma is one of the rare causes of polycythemia. We report a 13-year-old girl with primarily neurological symptoms identified to be polycythemic during routine evaluation. Clinical examination and neuroimaging subsequently confirmed an intracranial space occupying lesion which was excised. Hemoglobin level normalized after tumor excision. This case report emphasizes the need for thorough systemic evaluation including central nervous system examination in children identified to be polycythemic. Keywords: CNS tumor; hemangioblastoma; polycythemia.

Recurrent Tuberous Sclerosis Complex/Mammalian Target of Rapamycin Mutations Define Primary Renal Hemangioblastoma as a Unique Entity Distinct From Its Central Nervous System Counterpart.

ABSTRACT: Renal hemangioblastoma (HB) is a rare subset of HBs arising outside of the central nervous system (CNS), with its molecular drivers remaining entirely unknown. There were no significant alterations detected in previous studies, including von Hippel-Lindau gene alterations, which are commonly associated with CNS-HB. This study aimed to determine the real molecular identity of renal HB and better understand its relationship with CNS-HB. A cohort of 10 renal HBs was submitted for next-generation sequencing technology. As a control, 5 classic CNS-HBs were similarly analyzed. Based on the molecular results, glycoprotein nonmetastatic B (GPNMB) immunohistochemistry was further performed in the cases of renal HB and CNS-HB. Mutational analysis demonstrated that all 10 renal HBs harbored somatic mutations in tuberous sclerosis complex 1 ( TSC1 , 5 cases), TSC2 (3 cases), and mammalian target of rapamycin (2 cases), with the majority classified as pathogenic or likely pathogenic. The CNS-HB cohort uniformly demonstrated somatic mutations in the von Hippel-Lindau gene. GPNMB was strong and diffuse in all 10 renal HBs and completely negative in CNS-HBs, reinforcing the molecular findings. Our study reveals a specific molecular hallmark in renal HB, characterized by recurrent TSC/mammalian target of rapamycin mutations, which defines it as a unique entity distinct from CNS-HB. This molecular finding potentially expands the therapeutic options for patients with renal HB. GPNMB can be considered for inclusion in immunohistochemical panels to improve renal HB identification.

[Hypervascular Tumors such as Hemangioblastoma].

Hemangioblastomas are richly vascular tumors. Therefore, visualizing the vascular anatomy of their feeders and drainers is important for planning surgical excision. Preoperative three-dimensional computer graphic(3DCG)images are useful for determining the number, location, and course of their feeders and drainers.

Ultrasonography monitoring with Superb Microvascular Imaging during cerebrovascular surgery.

INTRODUCTION: Ultrasonography (US) is used as a real-time dynamic imaging modality during neurosurgery. A novel Doppler US technique, Superb Microvascular Imaging (SMI), can be used to visualize low-velocity flow of small vessels at high resolution with high frame rates. We visualized vessel flow using this US SMI technique and contrast agent during cerebrovascular surgery. METHODS: Forty-three patients with an unruptured cerebral aneurysm (control), ischemic and hemorrhagic moyamoya disease, carotid artery stenosis, hemangioblastoma, severe stenosis of the middle cerebral artery, venous angioma, and intracerebral hemorrhage (ICH) underwent neurosurgery with US SMI monitoring using a contrast agent. The diameter, length, and number of penetrating vessels were analyzed in patients with an unruptured cerebral aneurysm (control), moyamoya disease, and ICH. RESULTS: Diameter and length of cerebral penetrating vessels were significantly increased in patients with moyamoya disease and ICH compared to control patients. The number of penetrating vessels was increased in moyamoya disease patients compared to control and ICH patients. In hemorrhagic moyamoya disease, flow in the penetrating vessels originated from a deep periventricular point and extended to the cerebral surface. Pulsatile cerebral aneurysms during clipping surgery and carotid artery stenosis during carotid endarterectomy were easily identified by SMI. Drastically increased vessel flow in patients with a hemangioblastoma or a venous angioma was observed. CONCLUSION: Using the US SMI technique and contrast agent, we obtained useful flow information of the vascular disease structure and intracerebral deep small vessels during cerebrovascular surgery. Further quantitative analysis will be informative and helpful for cerebrovascular surgery.

A case report of cerebellar hemangioblastoma simulated brain metastasis shown by magnetic resonance imaging.

RATIONALE: Hemangioblastomas occur both sporadically and as an important component of von Hippel-Lindau (VHL) disease. The typical MRI features of hemangioblastoma are cysts with enhanced cystic wall nodules in the cerebellum or lesions with uniform enhancement on the surface or inside the spinal cord. If there is edema around hemangioblastoma, it is easy to be misdiagnosed as brain metastasis on MRI. PATIENT CONCERNS: A 41-year-old male patient was found to have a lump in the pancreas during a health examination 3 months ago. Subsequently, the patient underwent surgical treatment. The postoperative pathology suggests that the pancreatic lesion is a neuroendocrine tumor. The patient subsequently came to our hospital for consultation on further treatment plans. Abnormal signals were found in the right cerebellum during pituitary magnetic resonance imaging (MRI) before the development of a treatment plan for neuroendocrine tumors. Subsequently, the patient underwent cerebellar mass resection surgery. The pathological result after the surgery was hemangioblastoma. DIAGNOSIS: The patient underwent surgery to remove the tumor and was diagnosed with hemangioblastoma by pathological examination. Subsequently, the patient's genetic testing results confirmed the diagnosis of VHL syndrome. INTERVENTIONS: The patient underwent cerebellar mass resection surgery. OUTCOMES: The patient recovered after surgical resection. LESSONS: In this report, we emphasize the atypical MRI manifestations of hemangioblastoma. For patients with VHL syndrome-related hemangioblastoma, genetic testing is necessary for the patient and their family members.

ZEISS PLEX Elite 9000 Widefield Optical Coherence Tomography Angiography as Screening Method for Early Detection of Retinal Hemangioblastomas in von Hippel-Lindau Disease.

Purpose: To evaluate early detection of retinal hemangioblastomas (RHs) in von Hippel-Lindau disease (VHLD) with widefield optical coherence tomography angiography (wOCTA) compared to the standard of care in ophthalmologic VHLD screening in a routine clinical setting. Methods: We conducted prospective comparisons of three screening methods: wOCTA, standard ophthalmoscopy, and fluorescein angiography (FA), which was performed only in uncertain cases. The numbers of detected RHs were compared among the three screening methods. The underlying causes for the lack of detection were investigated. Results: In 91 eyes (48 patients), 67 RHs were observed (mean, 0.74 ± 1.59 RH per eye). FA was performed in eight eyes. Ophthalmoscopy overlooked 25 of the 35 RHs detected by wOCTA (71.4%) due to the background color of the choroid (n = 5), small tumor size (n = 13), masking by a bright fundus reflex (n = 2), and masking by surrounding retinal scars (n = 5). However, wOCTA missed 29 RHs due to peripheral location (43.3%). The overall detection rates were up to 37% on the basis of ophthalmoscopy alone, up to 52% for wOCTA, and 89% for FA. Within the retinal area covered by wOCTA, the detection rates were up to 46.7% for ophthalmoscopy alone, up to 92.1% for wOCTA, and 73.3% for FA. Conclusions: The overall low detection rate of RHs using wOCTA is almost exclusively caused by its inability to visualize the entire peripheral retina. Therefore, in unclear cases, FA is necessary after ophthalmoscopy. Translational Relevance: Within the imageable retinal area, wOCTA shows a high detection rate of RHs and therefore may be suitable to improve screening for RHs in VHLD.

Hemangioblastoma and arteriovenous malformation in the same patient: a not random association or two isolated entities? Systematic review starting from a unique case.

BACKGROUND: The association between intracranial hemangioblastomas and arteriovenous malformations has been documented in very few cases in literature since 1965 and might present in three modalities: "intermixed, adjacent and separated (spatially and temporally)". Often, the pattern of presentation is "intermixed". According to our systematic review, we propose an adjustment of the previous classification, specifically for these entities. We describe the first case of a truly "spatially separated" association between these two lesions. METHODS: Our study encompassed all adult patients diagnosed with both intracranial hemangioblastoma and AVM who were evaluated in the last 20-year period, from 2003 to 2023 at Helsinki University Hospital. Cases of this coexistence were retrospectively identified and collected from clinical records. For the systematic review, studies reporting the coexistence of hemangioblastoma and AVM in adult patients (>18 years old) were selected. Given the rarity of this pattern, case reports were also included. RESULTS: The combined analysis of our systematic review and institutional retrospective study revealed a total of only seven identified cases. We applied the classification of neoplasms and AVM by Yano, modifying and adapting it into our screened patient series. We systematically reclassified "adjacent" and genuinely "spatially separated" patterns based on the vascular axis supplying both lesions. CONCLUSIONS: Hemangioblastomas and AVMs rarely coexist in the same patient. Our study reports the first instance of a truly "spatially separated" sporadic association between these vascular lesions. The rarity of such coexistence underscores the need for a nuanced and systematic classification to guide the management of these infrequent cases.

Epidemiology and economic burden of Von Hippel-Lindau Disease-associated central nervous system hemangioblastomas and pancreatic neuroendocrine tumors in the United States.

BACKGROUND: To date, real-world evidence around the clinical and economic burden related to von Hippel-Lindau (VHL) disease is limited. Therefore, this study characterized the prevalence, healthcare resource utilization (HRU), and economic burden of von Hippel-Lindau-associated central nervous system hemangioblastoma (VHL-CNS-Hb) and pancreatic neuroendocrine tumors (VHL-pNET) in the United States (US). METHODS: Patients with VHL-CNS-Hb or VHL-pNET were identified from Optum's de-identified Clinformatics® Data Mart Database (2007-2020) and matched 1:5 to control patients without VHL disease or CNS-Hb/pNET. Prevalence rates of VHL-CNS-Hb and VHL-pNET (standardized by age and sex) in 2019 were estimated. HRU and healthcare costs (2020 US dollars) were compared between the VHL-CNS-Hb/VHL-pNET and control cohorts. RESULTS: In 2019, US prevalence rates of VHL-CNS-Hb and VHL-pNET were estimated to be 1.12 cases per 100,000 (3,678 patients) and 0.12 cases per 100,000 (389 patients), respectively. Patients with VHL-CNS-Hb (N = 220) had more inpatient, outpatient, and emergency department visits and $49,645 higher annual healthcare costs than controls (N = 1,100). Patients with VHL-pNET (N = 20) had more inpatient and outpatient visits and $56,580 higher annual healthcare costs than controls (N = 100). Costs associated with surgical removal of CNS-Hb and pNET were particularly high. CONCLUSIONS: In this retrospective, claims-based study, both VHL-CNS-Hb and VHL-pNET were associated with substantial HRU and healthcare costs, particularly tumor reduction surgery-related costs. These findings provide important insight for healthcare payers regarding the expected real-world costs that enrollees with VHL-CNS-Hb and VHL-pNET may incur over the course of their disease.

A novel presentation of diaphragmatic flutter in a patient with obstructive sleep apnea and recurrent cerebellar hemangioblastoma.

We report a unique case of diaphragmatic flutter in a patient with obstructive sleep apnea who had no respiratory symptoms related to flutter and a history of recurrent cerebellar hemangioblastoma. The flutter was detected during a routine follow-up monitoring through the built-in software of the positive airway pressure device; the flow and pressure curves showed abnormal and curious oscillations. The ultrasound confirmed the diagnosis and ruled out other causes of abnormal diaphragmatic movements. This case report contributes to the scientific literature by presenting a novel case of diaphragmatic flutter associated with recurrent cerebellar hemangioblastoma. It also emphasizes the need for more research on the pathophysiology and treatment of this rare condition. CITATION: Ciorba C, Espinoza Perez JA, Alfonso Imizcoz M, Errasti Viader J, Cebollero Rivas P, De Vito EL. A novel presentation of diaphragmatic flutter in a patient with obstructive sleep apnea and recurrent cerebellar hemangioblastoma. J Clin Sleep Med. 2024;20(2):313-317.

Al18F-NOTA-Octreotide PET/CT and 18F-FDG PET/CT for Detecting Cerebellar Hemangioblastoma in a Patient With Von Hippel-Lindau Disease.

ABSTRACT: Von Hippel-Lindau disease is a hereditary syndrome associated with various benign and malignant tumors, including hemangioblastomas. A 42-year-old man with a history of Von Hippel-Lindau disease underwent surgery for pancreatic neuroendocrine tumor and renal clear cell carcinoma and was recommended to undergo Al18F-NOTA-octreotide and 18F-FDG PETCT examination to assess potential metastases. 18F-FDG PET/CT showed low uptake in the right cerebellum, which demonstrated increased Al18F-NOTA-octreotide activity. Cerebellar mass resection surgery was performed. Pathological result was consistent with hemangioblastoma. This case report indicates the significant role of Al18F-NOTA-octreotide in the diagnosis of hemangioblastoma.

How I do it: cervical hemangioblastoma resection. Surgical technique and complication avoidance.

BACKGROUND: Spinal cord hemangioblastomas are benign, highly vascular neoplasms that affect the brain and, rarely, the spinal cord. They can be solitary or as part of von Hippel-Lindau syndrome. Radiosurgery is not a suitable treatment option. Endovascular embolization can only be adjunct to surgery. METHOD: We present a detailed approach to resection of a spinal cord hemangioblastoma. A video demonstrates the microsurgical technique and discusses complication avoidance. CONCLUSION: The pitfalls to consider are preservation of normal spinal cord vessels, protection of the pia-arachnoid cleavage plane, and avoidance of tumor piecemeal removal. Careful microsurgical resection and detailed preoperative planning are key.