Intraspinal primitive neuroectodermal tumor: imaging findings in six cases

Primary extraskeletal intradural Ewing sarcoma with acute hemorrhage: a case report and review of the literature

BACKGROUND

Spinal cord tumors present a challenge in diagnosis and treatment due to their varied histopathological characteristics. While Ewing sarcoma is a rare malignant tumor typically originating from skeletal bone, cases of primary intradural extraskeletal Ewing sarcoma are exceptionally rare. The similarity of its presentation to other spinal tumors further complicates its identification and management.

CASE PRESENTATION

We report a case of a 58-year-old Palestinian male with intradural extraskeletal lumbar Ewing sarcoma. The patient initially presented with lower back pain and bilateral S1 radiculopathy, with more severe symptoms on the left side. Magnetic resonance imaging revealed a 7 cm oval-shaped mass with homogeneous contrast enhancement, obstructing the spinal canal from L3/L4 to L5/S1 levels. Initially, a myxopapillary ependymoma was suspected, but the patient's sensory and motor functions suddenly deteriorated during hospitalization. Repeat magnetic resonance imaging indicated heterogeneous contrast enhancement, indicating acute intratumoral hemorrhage. Consequently, the patient underwent emergent L3-L5 laminotomy, with successful gross total resection of the tumor. Histopathological and immunohistochemical analyses confirmed the diagnosis of intradural extraskeletal Ewing sarcoma. Adjuvant therapy was administered to minimize the risk of local recurrence or distant metastasis. A systematic review of relevant literature, along with retrospective analysis of medical records, operative reports, radiological studies, and histopathological findings of similar cases, was also conducted.

CONCLUSIONS

Intradural extraskeletal Ewing sarcoma is an infrequently encountered condition in adult patients, emphasizing the importance of considering it in the differential diagnosis of spinal tumors. Surgeons must possess a comprehensive understanding of this rare entity to ensure accurate staging and optimal management, particularly in the early stages when prompt intervention may improve prognosis.

A case of giant Ewing's sarcoma (EES)/primitive neuroectodermal tumor (PNET) of the cervicothoracic junction in children with incomplete paralysis of both lower limbs: Case report and literature review

Background

Extraosseous Ewing's sarcoma/primary neuroectodermal tumor (EES/PNET) is a rare, malignant, small round blue cell tumor, which usually involves the larynx, kidneys, and esophagus. The most common metastatic sites are lung and bone. The incidence of epidural EES/PNET was 0.9%, and a detailed search of the PubMed literature found only 7 case reports of epidural ESS/PNET at the cervicothoracic junction in children.

Case description

We report a case of epidural ESS/PNET at the cervicothoracic junction in a child with chest and back pain as the first symptom, which worsened after half a year and developed incomplete paralysis of both lower extremities and urinary incontinence. She underwent emergency surgery, chemotherapy and radiotherapy, and died of lung metastases 8 months after surgery.

Conclusion

Primary epidural tumors are mostly benign, such as spinal meningiomas and neuromas. Contrary to what has been previously thought, we report a case of malignant epidural EES/PNET at the cervicothoracic junction without bone destruction; The rarity of epidural EES/PNET at the cervicothoracic junction in children has led to a lack of data, particularly on prognostic factors and recurrence patterns. Due to the difficulty of early diagnosis and high mortality, spine surgeons must explore and increase their awareness of this disease.

Primary Spinal Extradural Extraosseous Primitive Neuroectodermal Tumor/Ewing's Sarcoma: A Critical Analysis and Review

Primary spinal extradural Ewing's sarcoma/primitive neuroectodermal tumor (PNET) is rare malignant tumor of childhood and early adulthood. The World Health Organization classifies PNET as an undifferentiated round cell tumor arising from primitive neuroepithelial cell. It can be central or peripheral PNET depending on site of presentation. Usually, the presenting symptoms are chronic back pain and myelopathy. Overall prognosis and survival are dismal in spite of total surgical resection and adjuvant therapy. Because of the rarity and malignant behavior, definite management of spinal PNET has never been described. After review of medical record at Acharaya Vinoba Bhave Rural Hospital, Sawangi, India, we identified four patients of spinal PNET and were included in our study. Age at diagnosis ranging from 15 to 26 years old with mean age of 20 years old. All four cases were epidural in location, two of which were of Askin type tumor with spinal cord compression. Rural population with low literacy and financial constraints were the key reasons of late presentations at our hospital. Counseling and proper education regarding the disease are a must for early case detection and early treatment of those living in rural areas and suffers from financial constraints. Due to rarity of the disease and its poor prognosis, a well-organized multicentric controlled trial is required to formulate a standard guidelines in the management of this disease.

Analysis of Clinical, Imaging, and Pathologic Features of 36 Patients with Primary Intraspinal Primitive Neuroectodermal Tumors: A Case Series and Literature Review

BACKGROUND AND STUDY AIMS

 Primary intraspinal primitive neuroectodermal tumors (PNETs) account for ∼0.4% of all intraspinal tumors, but information about these tumors in the medical literature is limited to single case reports. We report four cases of primary intraspinal PNETs and present a systematic literature review of the reported cases.

MATERIALS AND METHODS

 We retrospectively reviewed and analyzed the clinical data of 4 patients with primary intraspinal PNETs who underwent neurosurgical treatment at our clinic between January 2013 and January 2020, and of 32 cases reported in the literature.

RESULTS

 The female-to-male ratio was 2.6:1. The mean patient age was 21.42 ± 15.76 years (range: 1-60 years), and patients <36 years of age accounted for 83.30% of the study cohort. Progressive limb weakness and numbness were the chief symptoms (accounting for ∼55.6%). The mean complaint duration was 0.89 ± 0.66 months for males and 2.72 ± 3.82 months for females (p = 0.028). Epidural (41.7%) was the most common site, and thoracic (47.3%) was the most frequent location. Most PNETs were peripheral, and magnetic resonance imaging (MRI) appearance was isointense or mildly hypointense on T1-weighted images and hyperintense on T2-weighted images. Homogeneous contrast enhancement was observed. The 1-year survival rate of patients who underwent chemoradiation after total or subtotal lesion resection was better compared with patients who did not undergo chemotherapy, radiotherapy, or total or subtotal resection. The modality of treatment was associated with survival time (p = 0.007).

CONCLUSION

 Primary intraspinal PNETs mainly occur in young people with a female preponderance. In patients with a rapid loss of lower limb muscle strength and large intraspinal lesions on MRI, PNETs should be considered. Surgical resection and adjuvant radio chemotherapy are key prognostic factors.

Multifocal primary central nervous system Ewing sarcoma presenting with intracranial hemorrhage and leptomeningeal dissemination: illustrative case

BACKGROUND

Ewing sarcoma is a neoplasm within the family of small round blue cell tumors and most frequently arises from skeletal bone. Primary involvement of the central nervous system in these lesions is extremely rare, with an incidence of 1%.

OBSERVATIONS

A case is presented of a 34-year-old man who presented with left facial numbness, multiple intracranial lesions, a lumbar intradural lesion, and diffuse spinal leptomeningeal involvement. A lumbar laminectomy and biopsy were performed, which revealed the diagnosis of extraskeletal Ewing sarcoma/primitive neuroectodermal tumor. The patient had a rapidly progressive clinical decline despite total neuroaxis radiation and multiple lines of chemotherapeutic treatments, eventually dying from his disease and its sequelae 6 months after diagnosis.

LESSONS

The authors' review of 40 cases in the literature revealed only 2 patients with isolated intraaxial cranial lesions, 4 patients with cranial and spine involvement, and an additional 34 patients with spine lesions. The unique characteristics of this patient's case, including his presentation with diffuse disease and pathology that included a rare V600E BRAF mutation, are discussed in the context of the available literature.

Primary Extraosseous Spinal Ewing Sarcomas: Should We Be More Aware About Diagnosis?

STUDY DESIGN

Single-center retrospective study.

OBJECTIVE

We discuss the widespread misdiagnosis of primary extraosseous spinal Ewing Sarcomas (PESES) to begnin tumors leading to poor treatment.

SUMMARY OF BACKGROUND DATA

PESES is a particular entity of spinal Ewing sarcoma (SES) appearing in a similar shape and features to benign tumors such as schwannomas. This imaging mimicry and subsequent possible misdiagnosis lead to primary surgery, without neoadjuvant chemotherapy, which remains deleterious for survival and progression.

METHODS

We identified a total of 13 patients: seven women (53.8%) and six men operated between 2001 and 2018 for PESES and initially misdiagnosed as schwannomas or ependymomas.

RESULTS

The mean age of our series was 35.8 years (range, 18.1-47.2 years). The first clinical symptom was neuralgia (61.5%) followed or associated with nerves deficits (38.5%). Median progression-free survival (PFS) was 31.7 months (SD 5.8). Tumor recurrence rates at 1 and 3 years were respectively 21.2% (SD 3.1) and 60.1% (SD 15.8). Median overall survival (OS) was 61.5 months (SD 16.27). The 1-year, 2-year, and 5-year survival estimates were 100.0%, 88.9% (SD 10.5), and 44.4% (SD 16.6). Six patients (46.13%) died following their SES. In univariate analyses, patients with metastastic PESES had a significantly lower OS than others (41.2 months, P = 0.03).

CONCLUSION

PESES must be ruled out at diagnosis of a spinal tumor when facing a fast-growing lesion with neurological deficits in a young adult. Thoracoabdominopelvic extension should be carried out. Presurgical biopsy must be performed. In case of PESES, neoadjuvant chemotherapy must be established before considering surgical intervention.Level of Evidence: 4.

Primary intradural extramedullary Ewing sarcoma: A case report and literature review

Tumors of the spinal cord and cauda equina show a wide spectrum of histology and require careful diagnosis and treatment. Primary intradural extramedullary Ewing sarcoma (IEES) is extremely rare, and initial imaging and clinical findings for this tumor mimic those of benign intradural spinal tumors. The present report describes a case of a 35-year-old woman who presented with IEES with meningeal seeding, and the literature on the management and clinical course of these tumors was reviewed. An examination revealed right-side leg dominant rapidly progressive hypoesthesia and motor deficits. MRI identified intradural tumors at the T12-L1 and L4-5 levels. Growth and an increase in the number of intradural tumors occurred over 3 weeks. Gadolinium-contrast T1-weighted MRI revealed diffusely enhanced signals for tumorous lesions with meningeal seeding in the cervical and thoracic spinal cord. Excision of a tumor at T12-L1 was performed to alleviate the symptoms and to make a histologic diagnosis. Microscopically, the tumor consisted of dense sheets of small round cells. Immunohistochemically, tumor cells showed intense and diffuse positive staining for CD99, ETS transcription factor ERG and Fli-1 proto-oncogene, ETS transcription factor (FLI1). The sequence analysis revealed the EWS RNA binding protein 1-FLI1 fusion transcript. The lesion was diagnosed as primary intradural ES. Adjuvant chemotherapy following radiotherapy for the whole spine was performed; however, multiple brain metastases were found at 10 months after diagnosis and the patient died of diffusely disseminated disease limited to the central nervous system without evidence of distant metastases at 16 months after the initial diagnosis. In a literature review of IEES cases, the 1- and 5-year overall survival rates were 79.8 and 26.6%, respectively, and the 1-, 2- and 5-year progression-free survival rates were 61.0, 52.3 and 10.9%, respectively. Therefore, primary IEES has a poor prognosis compared with ES of bone, and novel agents and treatment strategies are required.

Ewing Sarcoma of the Cervical Epidural Space Presenting with Tetraplegia: Case Report and Review of Literature

BACKGROUND

Ewing sarcoma (ES) is among the most frequented extremity osseous tumor in childhood. It was first described by James Ewing as diffuse endotheliomas in 1921. The name Ewing sarcoma was coined by Oberling in 1928 as a tribute to the legend who described this disease. ES exists in osseous and extraosseous forms. It shares much of its molecular typing with primitive neuroectodermal tumor (PNET); hence, they are regarded as different ends of the same molecular spectrum. ES, extraosseous ES, PNET, and Askins tumor are the other members of this family termed the Ewing sarcoma family of tumors. Extraosseous ES has been described in various locations of the spine, but its occurrence in the cervical epidural region is uncommon.

CASE DESCRIPTION

A 12-year-old child presented to us with neck pain and progressive weakness of all 4 limbs. She was investigated and found to have a highly vascular lesion in the cervical epidural region extending from C2 to the C4 region. Embolization therapy was unsuccessful. She deteriorated and eventually had to undergo emergency surgery to decompress the spinal cord. The lesion was biopsied and diagnosed as extraosseous ES. After radiotherapy and chemotherapy, the patient regained most of the power in her limbs.

CONCLUSION

Extraosseous ES is a rare tumor of the cervical cord in this age group. We report this case to highlight the difficulties encountered in the management of this variant.

Primary intraspinal extradural primitive neuroectodermal tumor: A rare case

Primitive neuroectodermal tumors (PNETs) are aggressive childhood malignancies and are difficult to treat. Primary intraspinal PNETs are rare. These patients have poor prognosis with short survival time even after surgery and chemoradiation. As there are no standard guidelines exist for the management of these tumors, a multidisciplinary approach has been employed with varying success. According to the review of literature, only few cases of primary intraspinal extradural PNETs have been reported. Herein, author has described a case of intraspinal, extradural PNET.

Imaging findings of adrenal primitive neuroectodermal tumors: a series of seven cases

OBJECTIVE

To explore the imaging features of adrenal primitive neuroectodermal tumors (PNETs).

MATERIALS AND METHODS

This retrospective study included seven patients with surgically and pathologically confirmed adrenal PNETs. Among them, six underwent computed tomography (CT) scans, and one underwent magnetic resonance imaging. The imaging findings, including size, shape, margin, hemorrhage, calcification, cystic degeneration, regional lymph nodes involvement, tumor thrombus formation and enhancement pattern, were retrospectively analyzed.

RESULTS

Among the seven adrenal PNET patients, six were male, and one was female. The median age was 26 years (range 2-56 years). The disease generally presented with either insidious symptoms (n = 4) or non-specific symptoms, including right flank pain (n = 1) and left upper abdominal discomfort (n = 2). On the pre-enhanced CT images, the tumor usually appeared as a well-defined, rounded or oval, heterogeneous mass without calcification. Certain tissue characteristics, such as cystic degeneration (n = 5), capsule (n = 4) and hemorrhage (n = 2), were observed. Regional lymph node involvement was observed in three cases, and renal vein thrombus was observed in one case. All cases showed mild heterogeneous enhancement of the tumor on the enhanced CT images.

CONCLUSION

An adrenal PNET commonly presents as a relatively large, well-defined, heterogeneous mass with cystic degeneration, necrosis and a characteristic mild contrast-enhancement pattern on multiphase enhanced images. PNET should be considered when the diagnosis of common tumors is not favored by signs on images.

CLINICAL TRIAL REGISTRATION STATEMENT

This study was approved by the medical ethics committee of Xiangya Hospital, Central South University. The approval number is 201512538.

Peripheral primitive neuroectodermal tumors of the spine: a case report and review of the literature

Background

Peripheral primitive neuroectodermal tumors are extremely rare tumors in the spine; only 18 cases of extra-dural peripheral primitive neuroectodermal tumor cervical region have been reported. The aim of this report is to highlight the challenges in diagnosis and management of this condition.

Case presentation

We present a case of 5-year-old Moroccan boy, who presented with torticollis for 1 month. Computed tomography scan and Magnetic resonance imaging of the cervical spine revealed an extradural, dumbbell-shaped mass with extra-spinal extension at the left C1–C6 level. Multiple biopsy specimens were obtained. Histological examination revealed a highly cellular neoplasm composed of diffuse sheets of tumor cells having monomorphic, round to oval, finely vesicular nuclei. Immunohistochemical findings confirmed the diagnosis of intraspinal peripheral primitive neuroectodermal tumor.

Conclusion

After this illustrative case, we review the literature on clinicopathological and therapeutic aspects. In practice, it is important to consider the diagnosis of peripheral primitive neuroectodermal tumor in children and adolescents with an apparent soft-tissue mass located in the spine.

Adult Primary Spinal Epidural Extraosseous Ewing's Sarcoma: A Case Report and Review of the Literature

Background. Extraosseous Ewing's sarcoma in the spinal epidural space is a rare malignancy, especially in adults. Case Presentation. A 40-year-old male presented with back pain and urinary hesitancy. MRI revealed a thoracic extradural mass with no osseous involvement. He underwent surgery for gross total resection of the mass, which was diagnosed as Ewing's sarcoma. He was subsequently treated with chemoradiotherapy. He remains disease-free 1 year after surgery. Review of the literature indicated only 45 previously reported cases of spinal epidural extraosseous Ewing's sarcoma in adults. Conclusions. Extraosseous Ewing's sarcoma in the spinal epidural space is a rare clinical entity that should be included in the differential for spinal epidural masses. Its treatment is multidisciplinary but frequently requires surgical intervention due to compressive neurologic symptoms. Gross total resection appears to correlate with improved outcomes.

Primary spinal primitive neuroectodermal tumor on MR imaging

Neoplasms in the region of filum terminale are not uncommon. Myxopapillary ependymoma is the commonest tumor at this location. The differentials reported for this entity are nerve sheath tumor, meningioma, paraganglioma, intradural metastases, lymphoma, other varieties of ependymoma, subependymoma, astrocytoma, ganglioglioma, hemangioblastoma, and primitive neuroectodermal tumor (PNET). PNET may very rarely present as an intradural thoracolumbar mass. We present pre- and post-therapy magnetic resonance imaging (MRI) features of a patient with proven primary spinal primitive neuroectodermal tumor (PSPNET) of peripheral subtype.

Peripheral primitive neuroectodermal tumor: dynamic CT, MRI and clinicopathological characteristics--analysis of 36 cases and review of the literature

Background

The peripheral primitive neuroectodermal tumor (pPNET) is a rare malignant tumor originating from neuroectoderm. The accurate diagnosis is essential for the treatment of pPNET.

Methods

we performed the largest cases of retrospective analysis thus far to review the unique computed tomography (CT), magnetic resonance imaging (MRI), and clinicopathological features of pPNET. The tumor location, morphological features, signal intensity, contrast enhancement characteristics, and involvement of local soft tissues of 36 pPNETs were assessed.

Results

Our results showed that there were more men (25/36) than women pPNETs patients. Unenhanced MRI (16 cases) showed that 14 cases were isointense and 2 cases were hypointense on T1WI. Nine cases were isointense and 7 were hyperintense on T2WI. Most pPNETs had heterogeneous signal intensity with small necrosis (CT: 31/36; MRI: 14/16) as well as heterogeneous enhancement (CT: 34/30; MRI: 15/16). The tumors usually had ill-defined borders and irregular shapes (CT: 30/36; MRI: 15/16). Pathologic exam showed small areas of necrosis in all tumors.

Conclusions

The diagnosis of pPNET should be suggested in young men when the imaging depicts a single large ill-defined solid mass with small area of necrosis, especially for those whose images show iso-intense on T1WI and T2WI and have heterogeneous enhancement.

Clinical presentation and long-term outcome of primary spinal peripheral primitive neuroectodermal tumors

Primary spinal peripheral primitive neuroectodermal tumors (pPNETs) are extremely rare entities that predominantly occur in children and young adults. Few studies have reported more than three cases. There are no current optimum treatment strategies due to the paucity of data. Here, we present 13 patients (nine females and four males) with primary intraspinal pPNETs who were surgically treated from April 2008 to February 2014. Histopathologic findings revealed the expression of CD99 in all cases. Limb weakness was the most common initial symptom (11/13, 85 %). The tumors were located mainly at the cervical level (6/13, 46 %) and in the epidural space (10/13, 77 %). The radiological diagnosis was neurinoma or meningioma in most cases (10/13, 77 %). Gross total resection was achieved in 77 % (10/13) of patients. During a mean follow-up of 25.5 months, local relapse occurred in 8 (61.5 %) patients and distant metastases occurred in 8 (61.5 %) patients. The overall 1-year survival rate was 77 % (10/13), and the overall 2-year survival rate was 54 % (7/13). The 2-year survival rate was 57.1 % in patients with adjuvant chemotherapy and 50 % in those without chemotherapy. Gross total resection and adjuvant radiotherapy with or without chemotherapy demonstrated a longer survival period (1-year survival rate: 100 %; 2-year survival rate: 86 %). Our data showed that primary spinal pPNETs are extremely rare and aggressive tumors with a poor prognosis. Radical resection is advocated. Gross total resection combined with adjuvant radiation may help to significantly improve patient survival period. Chemotherapy may also help to slightly prolong patient life.

Radiological and clinicopathological features of pPNET

PURPOSE

To analyze the radiological and clinicopathological features of peripheral primitive neuroectodermal tumor (pPNET).

MATERIALS AND METHODS

We retrospectively reviewed the computed tomography (CT) and magnetic resonance (MR) imaging of 14 cases of pPNET confirmed immunohistochemically. Relevant clinical data was also obtained.

RESULTS

Of 14 cases, there were 10 male and 4 female with a mean age of 28 years. The main symptoms were the aggravated pain of the lesion site and enlarged palpable masses. Fourteen lesions were located in the chest wall (n = 4), retroperitoneum (n = 3), pelvic cavity (n = 2), intraspinal area (n = 2), nasal cavity (n = 1), leg ( n= 1) and iliac bone (n = 1). Eleven lesions originating from the soft tissue mainly demonstrated large and infiltrative mass with (n = 4) or without (n = 7) bony invasion. Ten cases of them showed heterogeneous density with patchy, necrotic foci and moderate heterogeneous enhancement. Four of them with large cystic area contained irregular septations within them. Two intraspinal cases had extradural lesions, extending through the intervertebral foramen and formed paraspinal soft tissue masses with vertebral destruction. The case within iliac bone demonstrated extensive mixed (lytic/osteoblastic) lesion with large adjacent soft tissue mass. After surgery or therapy, 10 patients died of local recurrences or metastases.

CONCLUSION

The diagnosis of pPNET should be suggested in young patient when imaging depicts a large, ill-defined, soft-tissue mass containing area of cystic degeneration with internal septations and extending along the neural route and nearby the middle of the trunk. The key for correct diagnosis is to inosculate imaging to clinical data.

Primary spinal extradural Ewing's sarcoma (primitive neuroectodermal tumor): Report of a case and meta-analysis of the reported cases in the literature

Background:

Primary spinal primitive neuroectodermal tumors (PNET) and/or spinal extraskeletal Ewing's sarcoma family tumors (ESET) are rare lesions appearing in the spinal extradural space. One hundred forty-one primary spinal PNETs, including 29 intramedullary lesions, have been reported in the literature. Encountering a case of primary epidural EES/peripheral PNET (pPNET) in sacral level, which is the fifth one occurring at this level in the literature, we have tried to conduct a meta-analysis of the reported cases.

Case Description:

A 44-year-old lady with epidural EES/pPNET is reported here. She was once operated for L5/S1 herniated disc, which did not ameliorate her symptoms. The clinical, imaging, surgical, and histopathologic characteristics of our case are presented and wide search of the literature is also done. All the reports were level 3 or less evidences and most of the series had missing parts. 106 cases of primary intraspinal (extradural/extramedullary-intradural) EES/pPNET and 29 cases of primary intramedullary PNET (CNS-PNET) have been reported in the literature. The most common clinical presentation in both entities was muscle weakness proportionate to the tumor location. Distant metastasis occurred in 38 of 99 (38%) cases of primary intraspinal EES/pPNET, while the rate of metastasis was 48% in patients with PNETs occurring in the intramedullary region (P > 0.05). One-year survival rate of the patients who underwent chemo-radiation after total or subtotal resection was better than those who did not receive chemotherapy or radiotherapy, or did not have total or subtotal resection. However, this difference was not repeated in 2-year survival rate in any of the tumor groups.

Conclusion:

It seems that total or subtotal removal of the tumor and adjuvant chemo- and radiation therapy can improve the outcome in these patients.

Magnetic resonance imaging characteristics of primary intraspinal peripheral primitive neuroectodermal tumour

PURPOSE

The purpose of our study was to describe the salient magnetic resonance imaging (MRI) findings in primary intraspinal peripheral primitive neuroectodermal tumour (PNET).

METHODS

A retrospective review of the clinical and MRI images of 7 pathologically proven cases of intraspinal peripheral PNETs was performed. The various parameters, such as vertebral level of involvement; tumour location, size, focality, and margin; signal intensity of the lesion; the presence of hemorrhage or calcification; any signal voids; assessment of the adjacent cord for cord compression; cord dilatation; the presence of paraspinal tissue mass; or vertebral or other bony changes, were analysed.

RESULTS

All 7 patients had lesions in the thoracolumbar region. Three patients had extradural lesions, 4 had intradural extramedullary lesions, and none had intramedullary lesions. Six lesions were well circumscribed. Only 1 patient had multifocal involvement. All lesions were of hypointense or isointense signal on T1-weighted imaging, whereas all but one were hyperintense on T2-weighted imaging. Lesions enhanced heterogeneously except 1 intradural extramedullary lesion, which enhanced homogeneously. A paraspinal mass was noticed in 2 patients. Vertebral collapse was present in 1 patients.

CONCLUSION

Intraspinal peripheral PNETs are rare spinal tumours. Although imaging characteristics are not specific, a focal circumscribed lesion in a young individual at the intramedullary, extramedullary intradural, or extradural spinal location that shows hypointense and hyperintense signal on T1- and T2-weighted images, respectively, requires PNET to be considered in the differentials.

Cytologic and immunohistochemical characterization of a primitive neuroectodermal tumor in the brain of a dog

A 6-year-old intact female Pointer dog was presented for evaluation of acute onset of ataxia, circling, and head tilt. Neurologic assessment revealed overall decreased postural reaction, left-sided hemiparesis with incoordination, rigidity of fore- and hindlimbs, strabismus of the right eye, and bilateral horizontal nystagmus. Using magnetic resonance imaging, a mass lesion was identified in the cerebrum adjacent to the left side of the cerebellum compressing the brain stem ventrally. The mass was incompletely resected, and during surgery fine-needle aspiration and biopsy of the mass were performed. Cytologically, smears were highly cellular and contained predominantly small to medium-sized discrete round cells with high nuclear to cytoplasmic ratios and round nuclei with rare deep clefts or indentation, smooth chromatin, and indistinct nucleoli. Numerous cytoplasmic fragments were noted in the background. The primary diagnosis was lymphoma; other differential diagnoses included neuroendocrine tumor and poorly differentiated tumor of neural origin. The histologic diagnosis was lymphoma, and the lesion was presumed to be metastatic. On immunohistochemical analysis, the cells expressed neither CD3 nor CD79a. Re-examination of the histologic section revealed disorganized sheets of cells with multifocal palisading and perivascular arrangements of rosette-like structures. An expanded panel of antibodies to vimentin, cytokeratin, glial fibrillary acid protein (GFAP), neuron-specific enolase (NSE), synaptophysin (SYN), S-100, and CD45 was applied to histologic sections. Neoplastic cells were immunoreactive for vimentin, NSE, and S-100. Based on the histologic appearance and immunophenotype of the tumor, a diagnosis of primitive neuroectodermal tumor (PNET) was made. PNET, although rare in dogs, should be considered as a differential diagnosis for round cell tumors in the brain.