Feline Facial Spindle Cell Tumors in 29 Cats: Histomorphological and Immunohistochemical Characterization

Soft tissue tumors/sarcomas (STSs) in felines, encompassing a variety of mesenchymal tumors with similar histomorphological features, present diagnostic challenges due to their diverse cellular origins and the overlap with other tumor types such as feline sarcoid. This study aimed to delineate the clinical, histomorphological, and immunohistochemical characteristics of 34 feline facial spindle cell tumors affecting 29 cats, including testing for bovine papillomavirus type 14 (BPV14), the virus causing feline sarcoids. Only five out of 12 tumors previously diagnosed as feline sarcoids based on histomorphology were confirmed by PCR for BPV14, underscoring the importance of comprehensive diagnostic approaches to accurately distinguish between STSs and feline sarcoids. This study shows that most facial spindle cell tumors were compatible with peripheral nerve sheath tumors (PNSTs) based on positive immunohistochemical staining for Sox10 and other immunohistochemical markers such as GFAP, NSE, and S100. Some of these tumors displayed as multiple independent masses on the face or as erosive and ulcerative lesions without obvious mass formation, an atypical presentation and an important highlight for general practitioners, dermatologists, and oncologists. This study also describes periadnexal whorling of neoplastic cells as a novel histomorphologic finding in feline facial PNSTs and emphasizes Sox10 as a useful complementary immunohistochemical marker for the diagnosis of facial PNST in cats, providing valuable insights for veterinary pathologists.

Systematic Characterization of the Clinical and Pathological Features of Schwannomas Harboring SH3PXD2A::HTRA1 Fusion

The understanding of schwannoma tumorigenesis has been reshaped by the recent identification of SH3PXD2A::HTRA1 fusion in 10% of intracranial/spinal schwannomas. Nonetheless, pathologic features of schwannomas harboring this fusion, as well as its prevalence outside intracranial/spinal locations, have not been characterized. We screened 215 consecutive schwannomas for their clinicopathologic characteristics and fusion status using reverse-transcriptase polymerase chain reaction (RT-PCR). Among 29 (13.5%) fusion-positive schwannomas, the most prevalent location was peripheral somatic tissue (30.7%, 19/62), followed by spinal/paraspinal (18.4%, 7/38), body cavity/deep structures (10%, 2/20), intracranial (1.3%, 1/75), and viscera (0/13). All 8 cellular, 4 microcystic/reticular, and 3 epithelioid schwannomas were fusion-negative, as were 41/42 nonschwannomatous peripheral nerve sheath tumors. Remarkably, a distinct 'serpentine' palisading pattern, comprising ovoid/plump cells shorter than usual schwannian cells in a hyalinized stroma, was identified in most fusion-positive cases and the schwannomatous component of the only fusion-positive malignant peripheral nerve sheath tumor. To validate this finding, 60 additional cases were collected, including 36 with (≥10% arbitrarily) and 24 without appreciable serpentine histology, of which 29 (80.6%) and 2 (8.3%) harbored the fusion, respectively. With percentages of 'serpentine' areas scored, 10% was determined as the optimal practical cut-off to predict the fusion status (sensitivity, 0.950; specificity, 0.943). Fusion positivity was significantly associated with serpentine histology, smaller tumors, younger patients, and peripheral somatic tissue, while multivariate logistic linear regression analysis only identified serpentine histology and location as independent fusion-predicting factors. RNA in situ hybridization successfully detected the fusion junction, highly concordant with RT-PCR results. Gene expression profiling on 18 schwannomas demonstrated segregation largely consistent with fusion status. Fusion-positive cases expressed significantly higher HTRA1 mRNA abundance, perhaps exploitable as a biomarker. In summary, we systematically characterize a series of 60 SH3PXD2A::HTRA1 fusion-positive schwannomas, showing their distinctive morphology and location-specific prevalence for the first time.

Schwannoma of the Sigmoid Colon: A Rare Case

Schwannoma is a type of peripheral nerve sheath tumor that is often found in the head and neck. Schwannomas in the digestive system, particularly the colon and rectum, are exceptionally rare, and they are mostly non-malignant and asymptomatic although sometimes patients can present with symptoms similar to those observed in patients with other gastrointestinal tumors like abdominal pain, fullness, nausea, vomiting, and change in bowel habits. For diagnosis and treatment, surgical resection along with biopsy is the gold standard. In this paper, we describe a rare case of sigmoid schwannoma that was successfully treated in our department by surgical resection.

Vaginal malignant peripheral nerve sheath tumor treated with complete surgical resection and postoperative radiation therapy

Malignant peripheral nerve sheath tumors (MPNSTs) are neoplasms originating from or differentiating into nerve sheaths of peripheral nerves. Vaginal origin is rare, with only six vaginal primary cases reported to date. A 55-year-old woman presented to our hospital with a 7 cm vulvar mass. Tumor biopsy results were suspicious of sarcoma, and pelvic magnetic resonance imaging and hysterofiberscopy showed that the tumor originated from the lower vagina. The mass was transvaginally excised, and histological examination confirmed the diagnosis of a vaginal MPNST with negative surgical margins. The patient underwent radiotherapy because the risk of recurrence was high, owing to the large tumor size and high mitotic index. The patient remained recurrence-free for 1 year after the primary treatment. This is the first case of a high-risk vaginal MPNST that avoided early disease recurrence with additional radiotherapy after complete tumor resection.

Single Stage Nasal Reconstruction for Solitary Neurofibroma Isolated in the Columella

Neurofibromas are benign peripheral nerve sheath tumors that can originate from several elements of peripheral nerves, including axons, Schwann cells, endoneurial fibroblasts, and perineurial cells. The occurrence of a solitary neurofibroma in the external nose, especially that isolated in the nasal columella, is extremely rare. To the best of our knowledge, only 4 cases of solitary neurofibromas in the external nose have been reported in the English literature: on the nasal dorsum, tip, and pyriform aperture, all originating from the trigeminal nerve. We report the first case of a solitary neurofibroma isolated in the nasal columella, which we found in an otherwise healthy 42-year-old man. We completely resected this tumor with a negative resection margin and performed reconstruction with a bilateral spreader graft and caudal septal extension graft using autologous septal cartilage. The postoperative course was successful in both cosmetic and functional results, with no sensory changes at the 1-year follow-up. Surgical treatment for this lesion was challenging due to the cosmetically obvious location and high rate of recurrence. A review of the literature highlights the clinical and histological characteristics, differential diagnosis, and management of solitary neurofibroma of the external nose.

Metastatic Multifocal Malignant Peripheral Nerve Sheath Tumour in the Cervicothoracic Spinal Cord of a Dog Initially Mimicking Meningomyelitis

A nine year old cross-breed dog was presented with a two week history of ambulatory tetraparesis and proprioceptive ataxia affecting all four limbs. Meningomyelitis of Unknown Origin (MUO) was presumptively diagnosed based on the magnetic resonance imaging (MRI) findings and cerebrospinal fluid (CSF) analysis. The dog received a tapering dose of glucocorticoids and cyclosporine, showing significant improvement and the stabilization of the clinical signs for seven months. After this period, the dog showed an acute clinical deterioration and a follow-up MRI revealed new multiple lesions affecting different spinal nerve roots along the cervicothoracic spinal cord. Following euthanasia, a final diagnose of multiple malignant peripheral nerve sheath tumors (MPNSTs) was made based on the histopathological examination. MPNSTs can affect the cranial nerves, spinal nerves or the associated nerve roots at any location and can lead to secondary spinal cord compression. The aim of the present case report is to describe the clinical presentation and atypical MRI findings of a dog with histologically confirmed multiple MPNSTs. According to the reviewed literature, this is the first reported case of simultaneous MPNSTs in the cervicothoracic spinal cord of a dog.

A Rare Case of a Large Sinonasal Neurofibroma

A neurofibroma is a benign peripheral nerve sheath tumor. Its appearance in the nose and paranasal sinuses is extremely rare. We present the case of a 61-year-old female with a large sinonasal neurofibroma. The patient was referred to our department due to the findings of a large invasive lesion originating from the left sinus with extension to the adjacent structures on computed tomography. A thorough examination revealed a mass within the left nasal cavity and exophthalmos. The initial symptoms of the disease probably appeared three years ago when she reported that she developed facial swelling following dental work. In the following period and due to reported blurred vision, she consulted with several medical specialists without receiving a diagnosis, while later she visited an otorhinolaryngologist, complaining of ear fullness, and local treatment was prescribed. Due to persistent symptoms, the patient was finally referred for computed tomography. Upon arrival at our department, she underwent a biopsy, which revealed the existence of a neurofibroma. The patient underwent endoscopic resection of the tumor and remains under close follow-up with no signs of recurrence. Sinonasal neurofibroma is a rare condition that presents with non-specific symptoms and may take years to reach a diagnosis. Open or endoscopic surgical resection seems to offer satisfactory results; however, similar cases reported in the literature are scarce.

Case Report: A Novel Lateral Approach to the C7, C8, and T1 Intervertebral Foramina for Resection of Malignant Peripheral Nerve Sheath Neoplasia, Followed by Adjunctive Radiotherapy, in Three Dogs

This case report describes the diagnosis, management and outcome of three dogs with peripheral nerve sheath tumors (PNSTs) involving the brachial plexus, C7 (case 1), C8 (case 2), and C8 and T1 (case 3) spinal nerves and nerve roots with intrathoracic invasion. Surgical resection required thoracic limb amputation and removal of the first rib, facilitating a novel lateral approach to the spinal nerves and foramina in all cases. This was followed by hemilaminectomy and rhizotomy in cases 1 and 2. Adjunctive radiotherapy was then performed in all dogs. All three dogs regained a good quality of life in the short-term following surgery. Two were euthanased after 3 and 10 months, following detection of a pulmonary mass in one case and multiple thoracic and abdominal masses in the other. The third dog was alive and well at the time of writing (7 months post-surgery). This surgical approach facilitated good access and allowed gross neoplastic tissue to be resected. The ease of surgical access was dependent, to a degree, on the size of the patient. This surgical approach can be considered in cases of PNSTs involving the caudal cervical or cranial thoracic spinal nerves and nerve roots. Adjunctive radiotherapy should be considered as part of a multi-modal approach to these challenging tumors due to the difficulty of achieving clean margins, particularly proximally, even with optimal surgical access.

Pelvic schwannoma in an adult male

Schwannomas are benign nerve sheath tumors that are generally encapsulated and commonly detected in the head, neck, and mediastinal regions. Schwannomas localizing in the pelvis are extremely rare and tend to be asymptomatic initially due to slow growth rate. Schwannomas may be misdiagnosed as urologic or gynecologic tumors. Pelvic schwannomas are typically solitary, large, and well-circumscribed masses in the retroperitoneum or presacral areas. Other imaging characteristics are cystic degeneration, repeated hemorrhages, and calcifications. Calcification patterns can be punctate, speckled, curvilinear, or along the walls of the masses. We report a young man with a pelvic schwannoma with typical imaging features.

Hybrid peripheral nerve sheath tumor of parapharyngeal space having features of neurofibroma and schwannoma in an 8-year-old child - A rare entity

Tumors of the parapharyngeal space (PPS) are extremely rare inpediatric age group. Out of all head-and-neck neoplasms, PPS tumors comprise only 0.5%. Majority of neoplasms in poststyloid PPS are neurogenic tumors. Conventional benign peripheral nerve sheath tumor (PNST) includes neurofibromas, schwannomas and perineuriomas. Hybrid PNSTs are rare entities having combined features of more than one histologic type, and the World Health Organization Classification of Tumors of the Central Nervous System, in the latest 2016, 4^th edition, has recently recognized and published it. The most common hybrid tumor is schwannoma/perineuroma followed by neurofibroma/schwannoma and neurofibroma/perineuroma. Here, we are reporting a hybrid PNST which was completely excised and having combined features of neurofibroma and schwannoma, confirmed by both histopathologically and immunohistochemically, in an 8-year-old child, in PPS.

Difficulty Breathing or Just a Case of the Nerves? Incidental Finding of Primary Pleural Schwannoma in a COVID-19 Survivor

Schwannoma is a rare tumor that arises from the Schwann cells, which are specialized, myelin-producing cells of the peripheral nerve sheaths. As anatomic logic would dictate, these masses commonly occur in the skull base, cerebellopontine angle, and posterior spinal roots. Of this already rare entity, rarer still are the pleural schwannomas, representing approximately 1-2% of thoracic tumors. These tumors commonly affect adults with a propensity for the third and sixth decades of life and a comparative male predilection. Schwannomas are benign, indolent, and follow an asymptomatic course. As such, they often come to light incidentally. Here we report a case of primary pleural schwannomas in a 68-year-old female, found incidentally on a CT scan of the chest. To the best of our knowledge and literature review, no other similar case has been reported in our country, Pakistan. Around three weeks before her presentation, she was diagnosed with COVID-19. Her infection had run a mild course with quick recovery without the need for any hospitalization. Therefore, the manifestation of shortness of breath after resolution of all other symptoms prompted a further workup. Radiographic chest x-ray revealed an incidental finding of a large right upper lobe lung mass, slightly impinging on the trachea. This was followed by a chest CT scan at our radiological imaging facility, which showed a large, well-encapsulated, right upper lobe lung mass in the paraspinal apical location. She then underwent an image-guided biopsy of the aforementioned mass, pathological analysis of which was suggestive of a benign peripheral nerve sheath tumor (PNST) arising from the pleura (pleural schwannoma). She underwent right posterolateral thoracotomy with uneventful complete surgical removal of the pleural-based lung mass. Postoperative investigations included a chest x-ray that showed interval complete resection of the mass. Currently, she is asymptomatic and her clinical condition has improved with the successful resumption of her daily routine. Physicians thus need to keep pleural schwannomas in mind as a probable diagnosis of intrathoracic tumors. Indolent and asymptomatic, they are very amenable to surgical resection with little to no chances of recurrence in the long term. However, these patients should be closely followed with repeat imaging studies when symptomatic.

A Solitary Sigmoid Perineurioma in an Otherwise Healthy 30-Year-Old Male

Colorectal perineuriomas are rare benign fibroblastic polyps of the colon found on colonoscopy and usually present as a sessile polyp distal to the splenic flexure. We report a case of sessile sigmoid perineurioma in a young healthy male. He presented with chronic constipation and underwent colonoscopy, which showed a 3-4 mm sessile polyp in the sigmoid colon. Biopsy results were significant for a perineurioma. These polyps are peripheral nerve sheath tumors composed of bland spindle cells with ovoid nuclei in a whorling appearance. The differential diagnosis of these nerve sheath tumors includes ganglioneuromas, schwannomas, neuromas, neurofibroma, or Schwann cell hamartomas, and gastrointestinal stromal tumor (GIST). While these polyps are regarded as benign, it is prudent to rule out other tumors that have malignant potential.

Subcutaneous neurofibroma as a cause of lameness in a warmblood horse: Neurofibroma in a horse

A neurofibroma was excised from the subcutis on the medial side of the left thigh of a 15-year-old Warmblood gelding, which had shown lameness of the left hind limb. No other source of lameness was found. Two weeks after surgery, the horse was sound at a lameness examination.

Differentiation of peripheral nerve sheath tumors in patients with neurofibromatosis type 1 using diffusion-weighted magnetic resonance imaging

BACKGROUND

We sought to determine the value of diffusion-weighted (DW) magnetic resonance imaging (MRI) for characterization of benign and malignant peripheral nerve sheath tumors (PNSTs) in patients with neurofibromatosis type 1 (NF1).

METHODS

Twenty-six patients with NF1 and suspicion of malignant transformation of PNSTs were prospectively enrolled and underwent DW MRI at 3T. For a set of benign (n = 55) and malignant (n = 12) PNSTs, functional MRI parameters were derived from both biexponential intravoxel incoherent motion (diffusion coefficient D and perfusion fraction f) and monoexponential data analysis (apparent diffusion coefficients [ADCs]). A panel of morphological MRI features was evaluated using T1- and T2-weighted imaging. Mann-Whitney U-test, Fisher's exact test, and receiver operating characteristic (ROC) analyses were applied to assess the diagnostic accuracy of quantitative and qualitative MRI. Cohen's kappa was used to determine interrater reliability.

RESULTS

Malignant PNSTs demonstrated significantly lower diffusivity (P < 0.0001) compared with benign PNSTs. The perfusion fraction f was significantly higher in malignant PNSTs (P < 0.001). In ROC analysis, functional MRI parameters showed high diagnostic accuracy for differentiation of PNSTs (eg, ADCmean, 92% sensitivity with 98% specificity, AUC 0.98; Dmean, 92% sensitivity with 98% specificity, AUC 0.98). By contrast, morphological imaging features had only limited sensitivity (18-94%) and specificity (18-82%) for identification of malignancy. Interrater reliability was higher for monoexponential data analysis.

CONCLUSION

DW imaging shows better diagnostic performance than morphological features and allows accurate differentiation of benign and malignant peripheral nerve sheath tumors in NF1.

Large venous hemangioma of brachial plexus

In this report, we present a rare case of a vascular brachial plexus tumor. The patient was a 29-year-old woman with the chief complaint of progressive enlargement of a soft tissue mass in the left upper extremity, without any pain or sensory, motor, or neurologic deficits. The soft tissue mass had presented in the left deltopectoral groove eight years ago. However, the patient had not been evaluated in the past eight years and was only recently admitted to a referral hospital. After complete examination, she underwent surgery for a nerve sheath tumor of the brachial plexus.

Primary malignant peripheral nerve sheath tumors arising from the spinal canal invading the abdominal cavity in a dog

A 9-year-old neutered male Wire Fox Terrier presented with an 1-month history of hindlimb paresis. Magnetic resonance imaging revealed a contrast-enhanced mass at the level of the L2 vertebral canal. The dog became paraplegic with no deep perception of the hindlimbs, and the mass was surgically removed. The histopathological diagnosis was of a malignant peripheral nerve sheath tumor (MPNST). The dog suffered a relapse of right hindlimb ataxia at 225 days after the surgery. The dog died 434 days after the surgery. Necropsy found a large mass in the abdominal cavity invading from the L2-nerve. This is the first report of MPNST invading the abdominal cavity through the nerve root.

Somatic Mutations of lats2 Cause Peripheral Nerve Sheath Tumors in Zebrafish

The cellular signaling pathways underlying peripheral nerve sheath tumor (PNST) formation are poorly understood. Hippo signaling has been recently implicated in the biology of various cancers, and is thought to function downstream of mutations in the known PNST driver, NF2. Utilizing CRISPR-Cas9 gene editing, we targeted the canonical Hippo signaling kinase Lats2. We show that, while germline deletion leads to early lethality, targeted somatic mutations of zebrafish lats2 leads to peripheral nerve sheath tumor formation. These peripheral nerve sheath tumors exhibit high levels of Hippo effectors Yap and Taz, suggesting that dysregulation of these transcriptional co-factors drives PNST formation in this model. These data indicate that somatic lats2 deletion in zebrafish can serve as a powerful experimental platform to probe the mechanisms of PNST formation and progression.

Need for arthrodesis following facetectomy for spinal peripheral nerve sheath tumors: an institutional experience and review of the current literature

OBJECTIVE

Spinal peripheral nerve sheath tumors (PNSTs) are a group of rare tumors originating from the nerve and its supporting structures. Standard surgical management typically entails laminectomy with or without facetectomy to gain adequate tumor exposure. Arthrodesis is occasionally performed to maintain spinal stability and mitigate the risk of postoperative deformity, pain, or neurological deficit. However, the factors associated with the need for instrumentation in addition to PNST resection in the same setting remain unclear.

METHODS

An institutional tumor registry at a tertiary care center was queried for patients treated surgically for a primary diagnosis of spinal PNST between 2002 and 2016. An analysis focused on patients in whom a facetectomy was performed during the resection. The addition of arthrodesis at the index procedure comprised the primary outcome. The authors also recorded baseline demographics, tumor characteristics, and surgery-related variables. Logistic regression was used to identify factors associated with increased risk of fusion surgery.

RESULTS

A total of 163 patients were identified, of which 56 (32 had facetectomy with fusion, 24 had facetectomy alone) were analyzed. The median age was 48 years, and 50% of the cohort was female. Age, sex, and race, as well as tumor histology and size, were evenly distributed between patients who received facetectomy alone and those who had facetectomy and fusion. On univariate analysis, total versus subtotal facetectomy (OR 9.0, 95% CI 2.01-64.2; p = 0.009) and cervicothoracic versus other spinal region (OR 9.0, 95% CI 1.51-172.9; p = 0.048) were significantly associated with increased odds of performing immediate fusion. On multivariable analysis, only the effect of total facetectomy remained statistically significant (OR 6.75, 95% CI 1.47-48.8; p = 0.025).

CONCLUSIONS

The authors found that total facetectomy and cervicothoracic involvement may be highly associated with the need for concomitant arthrodesis at the time of index surgery. These findings may help surgeons to determine the best surgical planning for patients with PNST.

Malignant progression of a peripheral nerve sheath tumor in the setting of rhabdoid tumor predisposition syndrome

Malignant progression of a benign or low-grade tumor in individuals with germline alteration of SMARCB1 gene is not well characterized. In a family in which two carrier children had germline SMARCB1 mutations and atypical teratoid rhabdoid tumor, we report malignant progression of a nerve sheath tumor over a 7-year period in an affected adult family member. Prompt identification of the germline SMARCB1 alteration and the resultant rhabdoid tumor predisposition syndrome can help guide genetic counseling and surveillance in affected family members.

Programming of Schwann Cells by Lats1/2-TAZ/YAP Signaling Drives Malignant Peripheral Nerve Sheath Tumorigenesis

Malignant peripheral nerve sheath tumors (MPNSTs) are highly aggressive Schwann cell (SC)-lineage-derived sarcomas. Molecular events driving SC-to-MPNST transformation are incompletely understood. Here, we show that human MPNSTs exhibit elevated HIPPO-TAZ/YAP expression, and that TAZ/YAP hyperactivity in SCs caused by Lats1/2 loss potently induces high-grade nerve-associated tumors with full penetrance. Lats1/2 deficiency reprograms SCs to a cancerous, progenitor-like phenotype and promotes hyperproliferation. Conversely, disruption of TAZ/YAP activity alleviates tumor burden in Lats1/2-deficient mice and inhibits human MPNST cell proliferation. Moreover, genome-wide profiling reveals that TAZ/YAP-TEAD1 directly activates oncogenic programs, including platelet-derived growth factor receptor (PDGFR) signaling. Co-targeting TAZ/YAP and PDGFR pathways inhibits tumor growth. Thus, our findings establish a previously unrecognized convergence between Lats1/2-TAZ/YAP signaling and MPNST pathogenesis, revealing potential therapeutic targets in these untreatable tumors.

The role of nerve microenvironment for neurofibroma development

Deregulation of RAS signaling in Neurofibromatosis type 1 (NF1) results in the development of multiple neurofibromas, complex tumor of the peripheral nerves with no effective medical treatment. There is increasing evidences that neurofibroma initiates through loss of NF1 function in the Schwann cell lineage, followed by a cascade of interactions with other cell types in the surrounding tumor microenvironment. In NF1 patients, neurofibromas always develop along peripheral nerves and do not migrate to distant organs, including the central nervous system. In this study, we sought to identify the contributions of these peripheral nerves in neurofibroma formation. Using in vivo and in vitro three-dimensional (3D) culturing system, we show that peripheral nerves are absolutely required for neurofibroma tumorigenesis and report a novel 3D skin raft culture system for neurofibroma formation in vitro to decipher tumor pathogenesis. This interaction between neoplastic Schwann cells and their surrounding neural microenvironment has important implications for understanding early cellular events that dictate tumorigenesis. It also provides fertile ground for the elucidation of intrinsic and extrinsic factors within the nerve microenvironment that likely play essential roles in neurofibroma development and, therefore, viable therapeutic targets in neurofibroma therapy.

Comparison of hybrid 18F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging and positron emission tomography/computed tomography for evaluation of peripheral nerve sheath tumors in patients with neurofibromatosis type 1

Rapidly enlarging, painful plexiform neurofibromas (PN) in neurofibromatosis type 1 (NF1) patients are at higher risk for harboring a malignant peripheral nerve sheath tumor (MPNST). Fludeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) has been used to support more invasive diagnostic and therapeutic interventions. However, PET/CT imparts an untoward radiation hazard to this population with tumor suppressor gene impairment. The use of FDG PET coupled with magnetic resonance imaging (MRI) rather than CT is a safer alternative but its relative diagnostic sensitivity requires verification. Ten patients (6 females, 4 males, mean age 27 years, range 8–54) with NF1 and progressive PN were accrued from our institutional NF Clinic. Indications for PET scanning included increasing pain and/or progressive disability associated with an enlarging PN on serial MRIs. Following a clinically indicated whole-body FDG PET/CT, a contemporaneous PET/MRI was obtained using residual FDG activity with an average time interval of 3–4 h FDG-avid lesions were assessed for both maximum standardized uptake value (SUVmax) from PET/CT and SUVmax from PET/MR and correlation was made between the two parameters. 26 FDG avid lesions were detected on both PET/CT and PET/MR with an accuracy of 100%. SUVmax values ranged from 1.4–10.8 for PET/CT and from 0.2-5.9 for PET/MRI. SUVmax values from both modalities demonstrated positive correlation (r = 0.45, P < 0.001). PET/MRI radiation dose was significantly lower (53.35% ± 14.37% [P = 0.006]). In conclusion, PET/MRI is a feasible alternative to PET/CT in patients with NF1 when screening for the potential occurrence of MPNST. Reduction in radiation exposure approaches 50% compared to PET/CT.

Peripheral nerve sheath tumors of the upper extremity and hand in patients with neurofibromatosis type 1: topography of tumors and evaluation of surgical treatment in 62 patients

Objective: Neurofibromatosis type 1 (NF1) is an autosomal dominant tumor predisposition syndrome with a tendency to develop peripheral nerve sheath tumors (PNST). Plexiform neurofibromas (PNF) are detected in a high proportion of affected patients. The tumors can lead to severe disfigurement and are classified as precancerous. This study examines the surgical procedures that have been performed on large PNST of the upper limb and hand, and investigates whether a specific distribution pattern of the tumors can be detected in surgically treated cases.

Methods: Surgical procedures on the upper extremity and hand performed on patients with NF1 were evaluated at an interval of 25 years (1992–2016). Topography of the tumors was classified according to dermatomes. The number of interventions per patient, duration of operations, and complications of the interventions were registered. An overview of the surgical treatment of PNST of the upper limb and hand was obtained from the literature, with special consideration of the genetic background of treated tumors.

Results: One hundred and sixty-three surgical interventions on the upper limb and hand were performed in 62 patients with NF1 for the treatment of large PNST, predominantly PNF (age: mean value: 27.33 years, male: 33, female: 29; right side: 25, left side: 26, bilateral: 7). Surgical procedures lasted an average of 72.47 minutes. In approximately half of the patients, one surgical procedure was sufficient. Duration of stay in hospital was on average 7–11 days. Neurological complications were rarely noted and occurred only temporarily. There were no dermatomes affected by PNF with particular frequency. However, some dermatomes were more often simultaneously affected by a PNF at the same time as others.

Conclusion: Although the distribution pattern shows some accumulation of tumor localization, tumors are distributed evenly and show very variable size and extent in individual cases. Surgical treatment of PNF of the upper limb and hand helps alleviate the physical discomfort that these patients have from their disfiguring disease. Repeated interventions are necessary relatively often in order to adapt the tumorous region to the outline of the limb and to improve its function.

Pilomatrixoma of the Neck/Shoulder Region Mimicking a Rapidly Growing Neoplasm of Peripheral Nerve Sheath Origin in Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is an autosomal dominant hereditary disorder. Neurofibroma is the most common neoplasm of this disease. This lesion is characterized by circumscribed soft or knotty skin tumors derived from peripheral nerve sheath cells. Numerous other neoplasms have been described for this tumor predisposition syndrome. This case report adds the diagnostic and therapeutic procedures in the case of an NF1 patient in whom the rapidly growing, nodular, subcutaneous tumor initially led to the suspicion of a malignant neoplasm. The tumor proved to be pilomatrixoma, which closely adhered to a neurofibroma.

Magnetic Resonance Imaging Appearance of Schwannomas from Head to Toe: A Pictorial Review

Schwannomas are benign soft-tissue tumors that arise from peripheral nerve sheaths throughout the body and are commonly encountered in patients with neurofibromatosis Type 2. The vast majority of schwannomas are benign, with rare cases of malignant transformation reported. In this pictorial review, we discuss the magnetic resonance imaging (MRI) appearance of schwannomas by demonstrating a collection of tumors from different parts of the body that exhibit similar MRI characteristics. We review strategies to distinguish schwannomas from malignant soft-tissue tumors while exploring the anatomic and histologic origins of these tumors to discuss how this correlates with their imaging findings. Familiarity with the MRI appearance of schwannomas can help aid in the differential diagnosis of soft-tissue masses, especially in unexpected locations.

A Unique Case of Carotid Splaying by a Cervical Vagal Neurofibroma and the Role of Neuroradiology in Surgical Management

Carotid splaying, also known as the Lyre sign, is a widening of the carotid bifurcation due to the displacement of the internal carotid artery and the external carotid artery just distal to the point of divergence. This phenomenon is classically exhibited by highly vascularized carotid body tumors and, in rare cases, by cervical sympathetic chain schwannomas. Demonstration of the Lyre sign by a cervical vagal neurofibroma, however, is a unique occurrence that has not been previously documented in the literature.

Neurofibromas are slow growing, poorly vascularized soft tissue masses and are a hallmark of the autosomal dominant genetic disorder, neurofibromatosis type 1 (NF-1). While targeted genetic therapies are evolving, management is currently dependent on a case-by-case resection of tumors with specific indications for chemo and radiation therapy. These resections rely on magnetic resonance imaging (MRI) to visualize tumor location and infiltration, but even in the setting of an established NF-1 diagnosis, additional imaging can be beneficial in ruling out more precarious tumors and optimizing surgical outcomes.

In this case, a 25-year-old female with known NF-1 presented with an enlarging cervical mass that demonstrated splaying of the left internal and external carotid arteries on MRI. Due to the typical association of the Lyre sign with carotid body tumors, magnetic resonance angiography (MRA) was crucial in guiding surgical decision making. Carotid body tumors are highly vascularized, may compress carotid branches, and carry a high risk of intraoperative bleeding. They are best visualized with MRA, which assesses carotid splaying and patency, and demonstrates vascular blushing within the tumor. 

This patient's MRA demonstrated the Lyre sign, patency of all carotid vessels, and a lack of vascularity within the mass, thus lowering suspicion for a carotid body tumor. Intraoperative use of imaging results facilitated a successful resection of a soft tissue tumor with minimal blood loss and no complications. Postoperative histologic examination confirmed a neurofibroma and definitively ruled out a carotid body tumor. This case highlights the importance of utilizing MRA whenever carotid splaying is seen on MRI and supports the consideration of neurofibromas in the differential for this finding. 

Pediatric Non-vestibular Schwannoma

While the clinicopathologic features of pediatric vestibular schwannomas, often in the context of neurofibromatosis type 2 (NF2), have been well studied, there is less data regarding the characteristics of pediatric non-vestibular schwannomas (NVS). Additionally, the rate of loss of SMARCB1/INI1 expression in this population has not been systematically evaluated. Our institutional archives were searched for cases of NVS arising in patients 18 years or younger. Clinicopathologic features including SMARCB1/INI1 status were assessed for each case. Twenty-three NVS from 9 males and 13 females (age range, 2 months to 18 years) were identified, and sites included paraspinal (n = 10), head and neck (n = 6), extremities (n = 4), trunk (n = 1), mediastinum (n = 1), and retroperitoneum (n = 1); 22 cases were Antoni A predominant with 6 cases comprising solely Antoni A tissue. The mitotic rate of the tumors ranged from 0 to 10/10 high-power fields (HPFs), and 3 tumors had mitotic rates of ≥4 mitoses/10 HPFs. Two tumors showed plexiform architecture. No NVS showed diffuse atypia, calcifications, microcystic/reticular architecture, epithelioid morphology, pseudoglandular change, neuroblastoma-like features, or necrosis. All tumors tested (23/23) showed retained nuclear expression of SMARCB1/INI1. Follow-up was available in 21 patients (range 1 week to 194 months), and 5 tumors recurred. Pediatric NVS have a relatively homogeneous appearance with a predominance of Antoni A areas. Pathologists should be aware that schwannomas in this age group may be cellular with mitotic rates of ≥4/10 HPFs to avoid misclassification as a spindle cell sarcoma.

Clinical Features and Surgical Treatment of Schwannoma Affecting the Base of the Tongue: A Systematic Review

Introduction  Schwannomas of the head and neck account for 25–40% of all cases, with presentation at the base of the tongue as the most frequent site for intraoral tumors.

Objectives  Here, a systematic review was conducted to include 15 cases of patients with schwannoma of the base of the tongue.

Data Synthesis  Most patients presented with a single, painless, well-encapsulated nodule at the base of the tongue. These nodules were slow-growing, with an average of 13.3 months from onset to presentation. Most cases were accompanied by airway obstruction, indicated by symptoms of dysphagia, dysarthria, snoring, and sleep apnea. Overall, the histological studies were consistent with a benign schwannoma with a palisading Antoni A and Antoni B pattern without malignant changes in cell morphology. These tumors were treated via complete surgical excision, and all cases achieved full remission by final follow-up.

Conclusion  Surgical removal is the primary mode of treatment with excellent postoperative prognosis and rare instances of recurrence. Given the rarity of this tumor, this review of available case studies serves to comprehensively describe clinical presentation and surgical treatment approaches to tongue base schwannoma.

Ancient schwannoma of gingiva - A rare case report

Oral schwannomas (OSs) are rare benign tumors of oral cavity derived from peripheral nerve sheath, composed of proliferation of schwann cells in a characteristic pattern. AS are long-standing lesions which exhibit degenerative changes and atypia due to which they could be mistaken for malignancy. The mean age of occurrence of AS in oral cavity is 43 years, and no case of oral AS has been reported in a pediatric patient so far. Here, we present a rare case of AS of oral cavity in a 10-year-old male child.

Bovine Papillomavirus DNA and S100 Profiles in Sarcoids and Other Cutaneous Spindle Cell Tumors in Horses

Histopathologic differentiation between deep dermal or subcuticular equine sarcoids (ie, nodular sarcoids) and other spindle cell tumors in the dermis and subcutis such as peripheral nerve sheath tumors (PNSTs) can be challenging based on morphologic criteria alone. It has been proposed that polymerase chain reaction (PCR) for bovine papillomavirus (BPV) DNA and S100 immunohistochemistry be used as diagnostic tests to separate equine sarcoids from PNSTs. We reviewed 197 skin-associated spindle cell tumors (ie, soft tissue sarcomas), including PNSTs and sarcoids, received at the University of Florida between 1995 and 2013 and performed BPV PCR and S100 immunohistochemistry on archived paraffin-embedded tissues. We found that BPV DNA was demonstrable in 70% of the sarcoids, 59% of the PNSTs, 37% of the fibrosarcomas, and 22% of other tumors (myxosarcomas, fibromas, and other sarcomas) diagnosed on histomorphologic characteristics. Positive S100 staining was only seen in 12 tumors in the study (5 fibrosarcomas, 3 sarcoids, 2 PNSTs, and 2 other sarcomas). The results demonstrate that BPV is associated with many skin-associated spindle cell soft tissue tumors in horses in addition to sarcoids. S100 was rarely expressed in equine soft tissue sarcomas in the skin but was expressed in many tumor types, including PNSTs and sarcoids. Because 41% of the PNSTs classified by histomorphology in this study were BPV negative and 94% were S100 negative, it is reasonable to classify these as soft tissue sarcomas with nerve sheath tumor histomorphology rather than as either PNSTs or sarcoids.

Giant solitary ancient schwannoma of the pleura masquerading as bronchopneumonia

We report a 53-year-old female who presented with complaints of sudden onset breathlessness, cough with expectoration for 6 months, and a right lung base lesion in the chest X-ray, which was diagnosed and treated as bronchopneumonia by the family physician. High-resolution computed tomography of the chest was done which revealed a large heterogeneously enhancing mass in the right thoracic cavity. She underwent thoracotomy and was found to have a giant encapsulated and well-circumscribed mass arising from the pleura. Excision biopsy of the mass revealed it to be an ancient schwannoma. Ancient schwannoma of the pleura is a very rare entity. Complete surgical resection is curative.

Malignant Peripheral Nerve Sheath Tumor of the Infraorbital Nerve

The objective of this study is to report a large, rare, and ulcerative infiltrated skin lesion. Its diagnosis, therapeutic management, and progress are described. The patient is a 78-year-old white man, who presented with a 12-month ulcerative perforated lesion that had affected and infiltrated the skin, with easy bleeding. He had a history of hypertension, although controlled, was a 40-year smoker, had chronic atrial fibrillation, diabetes, and microangiopathy. During the consultation, the patient also presented with ocular obstruction due to an inability to open the eye. He mentioned having reduced vision. The computed tomography scan showed upper maxilla osteolysis without eye involvement. We underwent a radical resection in which upper maxilla and the anterior orbital margin were included. We used a Becker-type flap that allowed us to rebuild the cheek and to complete a modified neck dissection. Progress was favorable; the patient recovered ocular motility and his vision improved to 20/200. The final biopsy result was "malignant peripheral nerve sheath tumor, malignant schwannoma." Malignant schwannoma of the peripheral nerve is extremely rare. The total resection and reconstruction being completed in one surgery represented a challenge due to the difficulty in obtaining tissues in addition to the necessity of an oncological resection.

Malignant peripheral nerve sheath tumors of the eighth cranial nerve arising without prior irradiation

OBJECTIVE Malignant peripheral nerve sheath tumors (MPNSTs) of the eighth cranial nerve (CN) are exceedingly rare. To date the literature has focused on MPNSTs occurring after radiation therapy for presumed benign vestibular schwannomas (VSs), while MPNSTs arising without prior irradiation have received little attention. The objectives of the current study are to characterize the epidemiology, clinical presentation, disease course, and outcome using a large national cancer registry database and a systematic review of the English literature. Additionally, a previously unreported case is presented. METHODS The authors conducted an analysis of the Surveillance, Epidemiology, and End Results (SEER) database, a systematic review of the literature, and present a case report. Data from all patients identified in the SEER database with a diagnosis of MPNST involving the eighth CN, without a history of prior radiation, were analyzed. Additionally, all cases reported in the English literature between January 1980 and March 2015 were reviewed. Finally, 1 previously unreported case is presented. RESULTS The SEER registries identified 30 cases between 1992 and 2012. The average incidence was 0.017 per 1 million persons per year (range 0.000-0.0687 per year). The median age at diagnosis was 55 years, and 16 (53%) were women. Thirteen cases were diagnosed upon autopsy. Of the 17 cases diagnosed while alive, the median follow-up was 118 days, with 3 deaths (18%) observed. When compared with the incidence of benign VS, 1041 VSs present for every 1 MPNST arising from the eighth CN. Including a previously unreported case from the authors' center, a systematic review of the English literature yielded 24 reports. The median age at diagnosis was 44 years, 50% were women, and the median tumor size at diagnosis was 3 cm. Eleven patients (46%) reported isolated audiovestibular complaints typical for VS while 13 (54%) exhibited facial paresis or other signs of a more aggressive process. Treatment included microsurgery alone, microsurgery with adjuvant radiation, or microsurgery with chemoradiation. Sixty-one percent of patients receiving treatment experienced recurrence, 22% of which were diagnosed with drop metastases to the spine. Ultimately, 13 patients (54%) died of progressive disease at a median of 3 months following diagnosis. The ability to achieve gross-total resection was the only feature that was associated with improved disease-specific survival. CONCLUSIONS MPNSTs of the eighth CN are extremely rare and portend a poor prognosis. Nearly half of patients initially present with findings consistent with a benign VS, often making an early diagnosis challenging. In light of these data, early radiological and clinical follow-up should be considered in those who elect nonoperative treatment, particularly in patients with a short duration of symptoms or atypical presentation. These data also provide a baseline rate of malignancy that should be considered when estimating the risk of malignant transformation following stereotactic radiosurgery for VS.

Primary peripheral nerve sheath tumors of the thyroid gland: A case report and literature review

Primary peripheral nerve sheath tumors (PNSTs) of the thyroid gland are rare, with fewer than 30 cases reported in the medical literature to date. Primary PNSTs of the thyroid gland are classified into malignant and benign PNSTs. The benign PNSTs may be further subclassified into neurofibromas and Schwannomas. This is the case report of a 51-year-old male patient presenting with multiple primary PNSTs involving the left lobe of the thyroid gland. The patient underwent total excision of the thyroid gland and the pathological results indicated a Schwannoma with Antoni type A and B cells. The literature was reviewed briefly and, to the best of our knowledge, this is the first case report of multiple primary PNSTs of the thyroid gland.

An unusual case of schwannomatosis with bilateral maxillary sinus schwannomas and a novel SMARCB1 gene mutation

Schwannomas are benign tumors that arise from Schwann cells in the peripheral nervous system. Patients with multiple schwannomas without signs and symptoms of neurofibromatosis Type 1 or 2 have the rare disease schwannomatosis. Tumors in these patients occur along peripheral nerves throughout the body. Mutations of the SMARCB1 gene have been described as one of the predisposing genetic factors in the development of this disease. This report describes a patient who was observed for 6 years after having undergone removal of 7 schwannomas, including bilateral maxillary sinus schwannomas, a tumor that has not been previously reported. Genetic analysis revealed a novel mutation of c.93G>A in exon 1 of the SMARCB1 gene.

Microcystic pseudoglandular plexiform cutaneous neurofibroma

Glandular structures are well documented to appear in peripheral nerve sheath tumors. These epithelial elements are usually present in malignant peripheral nerve sheath tumors although a few cases of glandular benign peripheral nerve sheath tumors have also been described, most of them being schwannomas. A neurofibroma with glands is considered to be a rare type of divergent differentiation, but a neurofibroma containing gland-like or pseudoglandular structures have not, to our knowledge, been described. We report a 33-year-old patient with a well-demarcated dermal neoplasm, composed of neoplastic Schwann cells, perineurial-like cells and fibroblasts in a matrix with collagen fibers and myxoid areas. A part of the tumor consisted of microcystic gland-like spaces lined by flat cells. These cells were either S100 positive or negative, with no epithelial membrane antigen, cytokeratin or CD31 immunostaining. Recognition of the presence of pseudoglandular elements in neurofibromas is important to distinguish them from other tumoral lesions, some of them with malignant potential.

Intraparotid schwannoma: A rare case report

Pleomorphic adenomas are the most common tumors which present as parotid masses. Shwannoma (peripheral nerve sheath tumor) is a rare entity in this region. Very few schwannomas originate from the facial nerve and in the majority of these cases the tumor involves its intratemporal part. The following case is reported because it presented as an asymptomatic parotid swelling with normal seventh nerve function, which masqueraded as pleomorphic adenoma clinically, radiologically and cytologically. However, it turned out to be peripheral nerve sheath tumor on histopathological examination.

Sinonasal Tract Neurofibroma: A Clinicopathologic Series of 12 Cases with a Review of the Literature

Neurofibroma (NF), a benign peripheral nerve sheath tumor, is very uncommon in the sinonasal tract, with only a few reported cases in the English literature. Cases within the files of the authors' institutions confined to the sinonasal tract were compared to cases reported in the English literature (Medline 1966-2014). The 12 patients included 6 females and 6 males, aged 26-75 years (mean 46.2 years). The patients usually presented clinically with a mass lesion (n = 11), obstruction (n = 4) or pain (n = 3), with an average symptom duration of 42.9 months. Two patients had neurofibromatosis (NF1). Tumors involved the nasal cavity alone (n = 8), maxillary sinus alone (n = 2), or mixed sites (n = 2), with a range of 0.4-4.1 cm (mean 2.2 cm). The tumors were circumscribed, composed of spindled to wavy cells with curvilinear nuclei set in a background of collagenized stroma and mast cells. Nuclear palisading and perivascular hyalinization were not seen. Mitoses were scant. Pleomorphism, necrosis and increased cellularity were absent. By immunohistochemistry, the lesional cells were S100 protein, SOX10 and NFP positive, while CD34 highlighted the perineurium. INI1 was intact, with strong nuclear expression in all cases. All patients had surgical excision without recurrence (mean follow-up 8.6 years). The principle differential diagnoses include schwannoma, perineurioma, fibromatosis, and solitary fibrous tumor. NF of the sinonasal tract occurs in middle-aged patients without a gender predilection, usually with non-specific symptoms present for a long duration. Tumors are relatively large (mean 2.2), and usually affect one site only. Surgery is curative, with only 16.7 % NF1 associated. S100 protein, SOX10 and NFP highlight the Schwann cells, with CD34 highlighting the perineural fibroblasts.

Cells of origin in the embryonic nerve roots for NF1-associated plexiform neurofibroma

Neurofibromatosis type 1 is a tumor-predisposing genetic disorder. Plexiform neurofibromas are common NF1 tumors carrying a risk of malignant transformation, which is typically fatal. Little is known about mechanisms mediating initiation and identity of specific cell type that gives rise to neurofibromas. Using cell-lineage tracing, we identify a population of GAP43(+) PLP(+) precursors in embryonic nerve roots as the cells of origin for these tumors and report a non-germline neurofibroma model for preclinical drug screening to identify effective therapies. The identity of the tumor cell of origin and facility for isolation and expansion provides fertile ground for continued analysis to define factors critical for neurofibromagenesis. It also provides unique approaches to develop therapies to prevent neurofibroma formation in NF1 patients.

Subcutaneous soft tissue sarcoma with rhabdoid features in a dog

A nine-year-old male beagle dog had a white spherical mass in the subcutis of the left lumbar region. Microscopically, spindle to oval cells diffusely proliferated in the fibrous and myxoid stroma. Many neoplastic cells showed rhabdoid features or vacuolated cytoplasm. Immunohistochemically, the neoplastic cells were positive for vimentin and S100 and partly positive for neuron-specific enolase and glial fibrillary acidic protein but were negative for von Willebrand factor, desmin and α-smooth muscle actin. Ultrastructurally, the neoplastic cells had abundant cytoplasmic processes and desmosome-like structures. Cytoplasmic inclusions of rhabdoid-featured cells in HE sections were composed of aggregates of intermediate filaments, and cytoplasmic vacuoles were identified as an invagination of cytoplasm. Although malignant peripheral nerve sheath tumor was suggested according to these results, the present case was diagnosed as a soft tissue sarcoma with rhabdoid features due to a lack of identification of the basal lamina under electron microscopy.

Plexiform neurofibromatosis involving face and oral cavity

Plexiform neurofibromas (PNFs) are one of the most common and debilitating complications of neurofibromatosis type I (NF-I). They account for substantial morbidity, disfigurement, functional impairment and are life threatening. PNFs can also be subjected to transformation into malignant peripheral nerve sheath tumor (MPNST). This complication is refractory to treat due to paucity of effective therapies for malignant soft tissue sarcomas in general and also the delay in diagnosis from a preexisting tumor. We report a case of PNF of face involving oral cavity with literature review.

Primary malignant peripheral nerve sheath tumor of the pleural cavity: rapid progression

Malignant peripheral nerve sheath tumor (MPNST) accounts for 5-10% of all malignant soft tissue tumors. It often affects the extremities and abdominal cavity and very rarely develops in the thoracic cavity. The incidence in the general population is 0.001%. In our paper we would like to present a case report of a 74-year-old female patient with primary MPNST of the pleural cavity which was previously misdiagnosed as a non-small cell lung cancer. Despite the combined treatment, after four months the patient developed a secondary tumor in the contralateral pleural cavity which was also treated operatively.

Collision tumor of the palate: A rare case report

This case report presents an unusual swelling of the palate in a 61-year-old-male patient. Histopathologically, it revealed features of two separate adjacent lesions, a spindle cells lesion showing diffuse immune-positivity for S-100 protein and focal positivity to glial fibrillary acid protein and an osseous lesion with numerous trabaculae of bone, adipocytes and myxoid tissue confirming the diagnosis of collision tumor of benign peripheral nerve sheath tumor and osteoma. Extensive search of English literature shows no reported cases of peripheral nerve sheath tumor with osteoma. The probable histogenesis of this collision tumor is discussed in detail. The purpose of this case report is to document this rare case in the literature so as to increase the awareness of this entity.