Epithelioid malignant schwannoma. A study of 14 cases

Survival outcomes of malignant peripheral nerve sheath tumors (MPNSTs) with and without neurofibromatosis type I (NF1): a meta-analysis

INTRODUCTION

Malignant peripheral nerve sheath tumors (MPNSTs) are malignancies that demonstrate nerve sheath differentiation in the peripheral nervous system. They can occur sporadically or be associated with neurofibromatosis type 1 (NF1), an autosomal dominant neurocutaneous disorder, with up to 13% of patients developing MPNSTs in their lifetimes. Previous studies have suggested conflicting findings regarding the prognosis of NF1 for patients with MPNSTs. The elucidation of NF1 as an independent prognostic factor on mortality has implications for clinical management. We aim to investigate the role of NF1 status as an independent prognostic factor of overall survival (OS) and disease-specific survival (DSS) in MPNSTs.

METHODS

An electronic literature search of PubMed and MEDLINE was performed on studies reporting OS or DSS outcomes of MPNSTs with and without NF1. A grey literature search by reviewing bibliographies of included studies and review articles was performed to find pertinent studies. Data was extracted and assessed in accordance with the PRISMA guidelines. A meta-analysis was performed to calculate hazard ratios (HRs) using a random-effects model. The primary and secondary outcomes were all-cause and disease-specific mortality, respectively, with NF1 as an independent prognostic factor of interest.

RESULTS

A total of 59 retrospective studies involving 3602 patients fulfilled the inclusion criteria for OS analysis, and 23 studies involving 704 MPNST patients were included to evaluate DSS outcomes. There was a significant increase in the hazard of all-cause mortality (HR 1.63, 95% CI 1.45 to 1.84) and disease-specific mortality (HR 1.52, 95% CI 1.24 to 1.88) among NF1 as compared to sporadic cases. Subgroup analyses and meta-regression showed that this result was consistent regardless of the quality of the study and year of publication.

CONCLUSION

NF1 is associated with a substantially higher risk of all-cause and disease-specific mortality. This finding suggests that closer surveillance is required for NF1 patients at risk of developing MPNSTs.

Ovarian epithelioid malignant peripheral nerve sheath tumor with EWSR1-CREM fusion: A case report and literature review

Epithelioid malignant peripheral nerve sheath tumor (EMPNST) is a rare soft tissue sarcoma. The authors report the first case of EMPNST arising in the ovary (OEMPNST). A 7-year-old child underwent left salpingo-oophorectomy due to tumor rupture and the pathology suggested a juvenile granulosa cell tumor (JGCT). Six cycles of bleomycin, etoposide, and carboplatin were administrated. A second surgery was applied due to relapse 4 months after the last cycle of chemotherapy, and the pathology revealed JGCT with extensive abdominopelvic seedings even after interinstitutional consultation in two hospitals. Next-generation sequencing demonstrated EWSR1 exon12-CREM exon6 fusion with neurofibromatosis-2 gene deletion, and no mutation was detected in either FOXL2 or DICER1. However, pathology consultation in two other hospitals suggested the diagnosis of OEMPNST, and additional immunohistochemical (IHC) staining revealed positive H3K27me3. Nonetheless, she was treated with nine courses of chemotherapy but experienced a second recurrence of extensive abdominal metastases approximately 3 months after ceasing chemotherapy. Neither elevated tumor makers nor abnormal sex hormones level was noted since the initial presentation. Repeated cytoreductive surgery was conducted and IHC staining showed expression of SOX10, S-100, INI-1, and α-inhibin in tumor tissue. A final diagnosis of OEMPNST with EWSR1-CREM fusion was established, indicating that the probability of OEMPNST could not be excluded when treatment for JGCT showed poor response. A comprehensive evaluation including biological characteristics, morphology, IHC staining, and molecular features is vital in the differential diagnosis between JGCT and OEMPNST.

S100-negative epithelioid malignant peripheral nerve sheath tumor with possible perineurial differentiation

Epithelioid malignant peripheral nerve sheath tumor (MPNST) is a rare subtype of MPNST composed of epithelioid cells with abundant cytoplasm. Currently, strong and diffuse immunostaining for S100 protein and SOX10 is generally regarded as a characteristic feature of epithelioid MPNST. However, malignant tumors with epithelioid morphology that arise from a peripheral nerve or a pre-existing benign nerve sheath tumor should be regarded as epithelioid MPNSTs when they do not show characteristic features that definitively lead to other specific diagnoses. Here, we describe 3 cases of epithelioid MPNST in the peripheral nerve or schwannoma that was negative for S100 protein and SOX10 expression. Instead, these tumors were positive for EMA, GLUT1, claudin 1, and cytokeratin to varying degrees, while all of them retained SMARCB1 and H3K27me3 by immunohistochemistry. EMA, GLUT1, and claudin 1 are known markers of perineurial cell differentiation; thus, they could possibly represent epithelioid MPNST with perineurial cell differentiation.

A novel BRD4-LEUTX fusion in a pediatric sarcoma with epithelioid morphology and diffuse S100 expression

Malignant epithelioid soft tissue tumors encompass a wide spectrum of lesions. Among them, Epithelioid Malignant Peripheral Nerve Sheath Tumors (MPNST) constitute a distinct subgroup, accounting for <5% of all MPNST. Epithelioid MPNST are infrequently associated with neurofibromatosis type 1, occasionally arise in a schwannoma and show diffuse S100 and CD34 expression, often combined with INI-1 loss. However, the molecular mechanisms underlying the tumorigenesis of epithelioid MPNST remain largely unknown. We describe a case of a 10-year-old girl with an epithelioid malignancy of the orbit. The tumor proved positive for S100, CD34 and SOX10, and, although INI-1 expression was maintained, the overall features suggested the possibility of an epithelioid MPNST, arising in an unusual location. NGS analysis revealed a novel in-frame BRD4-LEUTX fusion gene. LEUTX plays an important role in embryonal genome activation and its expression is mostly suppressed postnatally. We were able to detect increased levels of LEUTX transcript in the tumor, indicating that BRD4-LEUTX fusion leads to LEUTX re-activation. To our knowledge, this fusion has never been reported previously. Whether the current case represents an example of epithelioid MPNST or a distinct tumor entity remains to be determined.

Pulmonary metastases from malignant epithelioid schwannoma of the arm presenting as fast-growing subsolid nodules: Report of an unusual case

Subsolid pulmonary nodules (SSNs) may be the manifestation of benign and malignant conditions. Malignant SSNs usually correspond to the preinvasive or invasive lepidic growth of pulmonary adenocarcinomas. More rarely, malignant SSNs may be the manifestation of primitive pulmonary lymphomas or metastases from extrapulmonary malignancies. In the case of metastases from extrapulmonary malignancies, the SSNs exhibit more aggressive behavior with rapid growth in a short period of time. The present article describes the first case of pulmonary metastases presenting as fast-growing SSNs in a patient with malignant epithelioid schwannoma of the arm.

Epithelioid Malignant Peripheral Nerve Sheath Tumor (Epithelioid-MPNST) Presenting as Bleeding Rectal Polyp: A Case Report with Systematic Literature Review

Case series

Patient: Male, 65 • Female, 47

Final Diagnosis: Epithelioid malignant peripheral nerve sheath tumor

Symptoms: Bleeding per rectum

Medication: —

Clinical Procedure: —

Specialty: Pathology

Vagal schwannomas of the head and neck: A comprehensive review and a novel approach to preserving vocal cord innervation and function

BACKGROUND

Schwannomas, benign tumors arising from neurolemmocytes, are the most common type of peripheral nerve tumors. Extracranial schwannomas are most often found in the parapharyngeal space, commonly involving the vagus nerve to cervical sympathetic trunk. Vagal schwannomas present several unique clinical and therapeutic challenges.

METHODS

A comprehensive literature review was conducted on 197 articles reporting 235 cases of cervical vagal schwannomas. Presenting symptoms, treatment approach, and postoperative outcomes were recorded and analyzed.

RESULTS

Vagal schwannomas commonly present as asymptomatic neck masses. When they become symptomatic, surgical resection is the standard of care. Gross total resection is associated with higher postoperative morbidity compared to subtotal resection. Initial reports using intraoperative nerve monitoring have shown improved nerve preservation. Recurrence rates are low.

CONCLUSION

The combination of intermittent nerve mapping with novel continuous vagal nerve monitoring techniques may reduce postoperative morbidity and could represent the future standard of care for vagal schwannoma treatment.

Metastatic Epithelioid Malignant Peripheral Nerve Sheath Tumor in a Known Case of Neurofibromatosis-1, Cytomorphological Appearance, and Critical Analysis of Immunohistochemistry

Malignant peripheral nerve sheath tumors (MPNSTs) are rare soft tissue tumors commonly arising from nerve roots in the extremities with a predilection in neurofibromatosis (NF) patients. MPNSTs are known to behave aggressively, with worse prognosis in nonresectable cases, and a 5-year survival of about 52% and 15% in resectable and unresectable cases, respectively. Although cytological diagnosis in a known case of NF-1 is possible, however, in the absence of any associated syndrome in a sporadic case, it is very challenging to accurately diagnose this tumor. Till date, to the best of our knowledge, only three cases of epithelioid MPNST correctly diagnosed on cytological examination have been described. We are presenting another case of epithelioid MPNST in a 40-year-old patient with stigmata of NF-1 since childhood, diagnosed on fine-needle aspiration cytology from the left flank mass with subsequent histopathology from left inguinal lymph node metastasis.

Synovial Sarcoma With a Predominant Epithelial Component

A case of synovial sarcoma of the lower leg in a 59-year-old woman with a predomi nant epithelial component is reported. Histologically, the tumor showed a well-devel oped epithelial component with a sheet-like and cribriform pattern with a sparsely distributed spindle cell component. Immunohistochemically, the epithelial component was positive for cytokeratins and epithelial membrane antigen, while the spindle cell component was positive for cytokeratins, epithelial membrane antigen, and vimentin. The epithelial component of synovial sarcoma is indistinguishable from carcinoma morphologically and immunohistochemically, therefore the presence of a biphasic pattern, even with a paucity of spindle cell component, is a crucial finding to establish a diagnosis of synovial sarcoma. The recognition and subclassification of this type of synovial sarcoma is important in arriving at a correct prognosis. Int J Surg Pathol 1(4): 261-268, 1994

Peripheral Nerve Sheath Tumors

This article presents an overview of the diagnostic categories of benign and malignant nerve sheath tumors, including neuroma, neurofibroma, nerve sheath myxoma, perineurioma, schwannoma, and malignant peripheral nerve sheath tumor. The discussion emphasizes histologic patterns; ancillary studies, such as immunohistochemistry; and differential diagnoses. The information is of value to practicing pathologists in both community and academic settings.

Huge epithelioid malignant peripheral nerve sheath tumor in the left axilla: a case report

This report describes a patient with a rare huge epithelioid malignant peripheral nerve sheath tumor (MPNST) in the left axilla. A male in his 70s was admitted to our hospital for evaluation of a growing tumor in his left axilla. The tumor was solid and immovable. Examination of a biopsy specimen resulted in a diagnosis of epithelioid MPNST. Two weeks after the biopsy was performed, the tumor grew to 20 cm and became painful, and the patient was unable to feel pressure on his upper arm. Immediately before surgery to remove the tumor, computed tomography suggested the presence of lung metastases. The patient and his family were informed of his disease state, and they elected surgical treatment to ease the symptoms associated with tumor enlargement. Systemic metastases appeared soon after the surgery, and the patient died within 11 weeks. Comparative genomic hybridization (CGH) analysis showed that this tumor was chromosomally unstable, with impairments in gene expression.

Cutaneous epithelioid malignant peripheral nerve sheath tumour: a clinicopathological analysis of 11 cases

AIMS

Epithelioid malignant peripheral nerve sheath tumour (E-MPNST) is a distinctive variant of malignant peripheral nerve sheath tumour characterized by the predominance of epithelioid cells, diffuse S100 positivity and infrequent association with neurofibromatosis type 1. The aim of this study was to further delineate clinicopathological features of cutaneous E-MPNST, correlate them with disease outcome and discuss differential diagnosis.

METHODS AND RESULTS

We analysed 11 cutaneous E-MPNSTs (six males, five females, median age 49 years, median size 1.6 cm). Tumours showed a predilection for lower extremities (45%) and trunk (45%), followed by upper extremity (9%). Follow-up was available for nine of 11 patients (range 24-100 months, median 52 months). Four patients had an uneventful clinical course (44%), two developed local recurrence(s) (22%) and three died due to disseminated disease (33%). No histological parameters were found to predict local recurrence(s), development of distant metastases or disease outcome, including size, percentage of epithelioid component, number of mitoses per 10 high-power fields, degree of nuclear atypia or site of occurrence (dermis, dermis/subcutis, subcutis) (P > 0.05). Immunohistochemically, all tumours were diffusely S100-positive, with a subset displaying loss of integrase interactor 1 (INI1) expression (50%).

CONCLUSIONS

Cutaneous E-MPNST has the potential to pursue an aggressive clinical course, associated with wide dissemination and unfavourable disease outcome.

Epithelioid malignant peripheral nerve sheath tumor: clinicopathologic analysis of 63 cases

Epithelioid malignant peripheral nerve sheath tumor (EMPNST) is rare and differs from conventional malignant peripheral nerve sheath tumor by showing diffuse S-100 protein positivity, infrequent association with NF1, and occasional origin in a schwannoma. Loss of INI1 expression is seen in a subset of tumors. The purpose of this study was to further define clinicopathologic features and outcome data in a large series of EMPNST. Sixty-three cases were identified in consultation files. The patient group consisted of 33 men and 30 women; the median age was 44 years (range, 6 to 80 y). One patient was reported to have NF1. One patient had 3 seemingly separate primary EMPNSTs during his 12-year clinical course. The median tumor size was 3.0 cm (range, 0.4 to 20 cm), and tumors were located most frequently on the lower extremity (30/63; 48%) and trunk (16/63; 25%). Most tumors were superficial (5 dermal, 38 subcutaneous); 15 were subfascial, and 5 were visceral. Microscopically, tumors comprised a relatively uniform but clearly atypical population of epithelioid cells. The majority of tumors demonstrated a multilobular growth pattern, with lobules and nests surrounded by myxoid and/or fibrous stroma. Tumor cells were round, polygonal, or ovoid and had round vesicular nuclei and abundant amphophilic to palely eosinophilic cytoplasm. Focal spindled morphology was seen in one third of cases. Most tumors (55/63; 87%) showed marked cytologic atypia with irregular vesicular nuclei and prominent nucleoli. Mitotic rate ranged from 1 to 46/10 HPF (median, 5/10 HPF); atypical mitotic figures were seen in 7 cases. Necrosis was present in 17 tumors. Twelve tumors were associated with a nerve. Nine tumors arose in a schwannoma (6 conventional type, 3 epithelioid) and 1 in a neurofibroma (in the NF1 patient). All tumors expressed S-100 protein, and the majority showed strong and diffuse staining (87%; 55/63). There was no expression of the melanocytic markers Mart-1/Melan-A (0/58), HMB-45 (0/57), and MiTF (0/9). Other immunohistochemical results included variable staining for GFAP (24/40; 60%) and EMA (4/29; 14%), whereas keratin was consistently negative (0/33). INI1 expression was lost in 67% of tumors examined (35/52). Most tumors were treated by surgical resection; 13 also received chemotherapy and/or radiation. Follow-up data were available for 31 cases and ranged in duration from 3 months to 20 years (median, 36 mo). Twenty-two patients have no evidence of disease at the time of follow-up. Nine patients developed local recurrence, 3 of whom were reported to be disease-free at the time of latest follow-up (44 mo, 19 y, and 20 y). Five patients developed distant metastases, and 4 patients died of disease (including 2 with unresectable recurrent tumors). Recurrence, metastasis, and disease-related death were observed independent of anatomic site or depth. In summary, EMPNST is a morphologically distinct variant that most commonly affects adults on the lower extremity or trunk, although a wide age range and site distribution are seen. Most tumors arise in superficial soft tissue, are diffusely S-100 positive, and two thirds show INI1 loss. On the basis of available follow-up information there is a comparatively low risk for recurrence and metastasis, irrespective of tumor depth.

Malignant epithelioid peripheral nerve sheath tumor with prominent reticular/microcystic pattern in a child: a low-grade neoplasm with 18-years follow-up

Malignant peripheral nerve sheath tumors (MPNSTs) constitute <2% of soft tissue neoplasms in children and display a wide histologic spectrum including low-grade and epithelioid variants, although most are high-grade spindle cell sarcomas. Here, we describe an unusual case of a large retroperitoneal epithelioid MPNST diagnosed in a 7-year-old girl without family history or clinical features of neurofibromatosis type 1. The patient was treated by repeated surgical interventions, polychemotherapy, autologous stem cell transplantation, and irradiation therapy. Over the years, she developed multiple disseminated abdominal recurrences but is currently alive with very slowly progressing disseminated intra-abdominal disease 18 years from initial diagnosis. Histologically, the tumor was composed of medium-sized polygonal and ovoid-to-spindled cells set within a copious myxoid matrix with a prominent reticular and microcystic pattern reminiscent of the recently described reticular/microcystic schwannoma. Immunohistochemistry revealed strong and diffuse expression of S100, CD56, CD57, collagen IV, and neuron-specific enolase, with negativity for perineurial cell markers (claudin-1, epithelial membrane antigen, and glucose transporter-1) and other lineage-specific mesenchymal and epithelial antigens. This unusual variant of low-grade MPNST must be differentiated from a variety of other entities, in particular benign perineurioma, myxoid neurofibroma, and benign reticular/microcystic schwannoma. Confinement of the recurrent disease to the abdominal cavity emphasizes the necessity of primary curative wide excision of this highly recurring but nonmetastasizing low-grade neoplasm.

Malignant epithelioid schwannoma of the oral cavity in a cat

A malignant epithelioid schwannoma of the oral cavity was diagnosed in an 8-year-old domestic short-hair cat. The mass was located in the gingiva of the upper left premolar to molar region and showed multinodular growth patterns. The mass comprised epithelioid cells arranged in densely packed sheets. Tumor cells had large, round to oval nuclei with prominent nucleoli and an abundant eosinophilic cytoplasm. Immunohistochemically, most of the tumor cells were positive for S-100 protein, glial fibrillary acidic protein and vimentin, but all lacked melanoma-associated antigen and muscle and neuroendocrine markers. Stains for type IV collagen showed linear immunoreactivity around single cells and groups of cells. Ultrastructurally, tumor cells were separated by a well-defined basement membrane, and interdigitating cell processes were observed. To our knowledge, this is the first report of feline malignant epithelioid schwannoma.

Survival meta-analyses for >1800 malignant peripheral nerve sheath tumor patients with and without neurofibromatosis type 1

There are conflicting reports as to whether malignant peripheral nerve sheath tumor (MPNST) patients with neurofibromatosis type 1 (NF1) have worse prognosis than non-NF1 MPNST patients. Large clinical studies to address this problem are lacking due to the rareness of MPNST. We have performed meta-analyses testing the effect of NF1 status on MPNST survival based on publications from the last 50 years, including only nonoverlapping patients reported from each institution. In addition, we analyzed survival characteristics for 179 MPNST patients from 3 European sarcoma centers. The meta-analyses including data from a total of 48 studies and >1800 patients revealed a significantly higher odds ratio for overall survival (OR(OS)) and disease-specific survival (OR(DSS)) in the non-NF1 group (OR(OS) = 1.75, 95% confidence interval [CI] = 1.28-2.39, and OR(DSS) = 1.68, 95% CI = 1.18-2.40). However, in studies published in the last decade, survival in the 2 patient groups has been converging, as especially the NF1 group has shown improved prognosis. For our own MPNST patients, NF1 status had no effect on overall or disease-specific survival. The compiled literature from 1963 to the present indicates a significantly worse outcome of MPNST in patients with NF1 syndrome compared with non-NF1 patients. However, survival for the NF1 patients has improved in the last decade, and the survival difference is diminishing. These observations support the hypothesis that MPNSTs arising in NF1 and non-NF1 patients are not different per se. Consequently, we suggest that the choice of treatment for MPNST should be independent of NF1 status.

Neurogenic tumors of soft tissue

Neurogenic tumors are an uncommon yet important category of soft tissue tumors in children and adolescents because of their frequent association with various genetic syndromes. The heterogeneous cellular composition of the peripheral nerve and the wide metaplastic capacity of the neural crest and its derivatives generate a variety of neoplasms with neurogenic differentiation. This article reviews the clinicopathologic features and differential diagnosis of neurogenic tumors in the first two decades of life, and highlights use of selected ancillary methods for diagnosis.

Pathology of peripheral nerve sheath tumors: diagnostic overview and update on selected diagnostic problems

Peripheral nerve sheath tumors are common neoplasms, with classic identifiable features, but on occasion, they are diagnostically challenging. Although well-defined subtypes of peripheral nerve sheath tumors were described early in the history of surgical pathology, controversies regarding the classification and grading of these tumors persist. Advances in molecular biology have provided new insights into the nature of the various peripheral nerve sheath tumors, and have begun to suggest novel targeted therapeutic approaches. In this review, we discuss current concepts and problematic areas in the pathology of peripheral nerve sheath tumors. Diagnostic criteria and differential diagnosis for the major categories of nerve sheath tumors are proposed, including neurofibroma, schwannoma, and perineurioma. Diagnostically challenging variants, including plexiform, cellular and melanotic schwannomas are highlighted. A subset of these affects the childhood population, and has historically been interpreted as malignant, although current evidence and outcome data suggest they represent benign entities. The growing current literature and the author's experience with difficult to classify borderline or "hybrid tumors" are discussed and illustrated. Some of these classification gray zones occur with frequency in the gastrointestinal tract, an anatomical compartment that must always be entertained when examining these neoplasms. Other growing recent areas of interest include the heterogeneous group of pseudoneoplastic lesions involving peripheral nerve composed of mature adipose tissue and/or skeletal muscle, such as the enigmatic neuromuscular choristoma. Malignant peripheral nerve sheath tumors (MPNST) represent a diagnostically controversial group; difficulties in grading and guidelines to separate "atypical neurofibroma" from MPNST are provided. There is an increasing literature of MPNST mimics which neuropathologists must be aware of, including synovial sarcoma and ossifying fibromyxoid tumor. Finally, we discuss entities that are lacking from the section on cranial and paraspinal nerves in the current WHO classification, and that may warrant inclusion in future classifications. In summary, although the diagnosis and classification of most conventional peripheral nerve sheath tumors are relatively straightforward for the experienced observer, yet borderline and difficult-to-classify neoplasms continue to be problematic. In the current review, we attempt to provide some useful guidelines for the surgical neuropathologist to help navigate these persistent, challenging problems.

INI1-deficient tumors: diagnostic features and molecular genetics

Significant progress has been made in understanding the molecular genetic alterations involved in sarcomagenesis. Cytogenetic and molecular studies have identified nonrandom genetic abnormalities, including tumor suppressor gene inactivation. Mutations, deletions, and other somatic alterations in the tumor suppressor gene INI1 (hSNF5; SMARCB1), which encodes a subunit of the SWI/SNF chromatin remodeling complex, were first described in the malignant rhabdoid tumor of infancy. Since then, INI1 has also been implicated in the pathogenesis of additional tumor types including renal medullary carcinomas and epithelioid sarcomas and a subset of epithelioid malignant peripheral nerve sheath tumors, myoepithelial carcinomas, and extraskeletal myxoid chondrosarcomas. As varied as this group appears, they all show loss of INI1 protein expression, a propensity for rhabdoid cytomorphology, and sometimes other overlapping immunohistochemical and histologic findings. We will review the clinicopathologic features of these tumor types and emphasize the clinical utility of INI1 immunohistochemistry in differential diagnosis.

Advanced epithelioid malignant peripheral nerve sheath tumor showing complete response to combined surgery and chemotherapy: a case report

Malignant peripheral nerve sheath tumor (MPNST) is a rare high-grade soft tissue sarcoma. The epithelioid variant accounts for 5% or less of MPNSTs; the clinical behavior of this variant is unclear. Reports of approximately 40 cases are available in the English literature; however, most reports addressed clinicopathological features rather than therapeutic procedures or clinical courses. We describe a case of a 62-year-old male with an epithelioid MPNST of the left foot. Multiple lung metastases developed after radical surgery on the primary lesion. The response to adjuvant chemotherapy including doxorubicin and ifosfamide was favorable, and thoracoscopic resection was subsequently performed on the remaining three metastases. No evidence of recurrence or metastasis was observed at the 12-month followup after the first operation. Further followup and chemotherapy may be required.

Epithelioid Lesions

Epithelioid variants have been described for most mesenchymal tumors, including leiomyosarcoma, pleomorphic liposarcoma, epithelioid fibrous histiocytoma, and myxofibrosarcoma. Soft tissue tumors that commonly show epithelioid morphology include epithelioid vascular lesions, epithelioid sarcoma, sclerosing epithelioid fibrosarcoma, and epithelioid malignant peripheral nerve sheath tumor. Many of the entities described in this review were originally described as "simulating carcinoma" or "often mistaken for carcinoma" and this pitfall should be considered when evaluating epithelioid lesions in soft tissue. Many epithelioid soft tissue tumors express epithelial antigens to a varying degree and an immunohistochemical panel is essential for correct classification.

A small intraneural epithelioid malignant peripheral nerve sheath tumour of the median nerve simulating a benign lesion: description of a case and review of the literature

The epithelioid variant of malignant peripheral nerve sheath tumours (MPNSTs) is a very rare malignancy. We describe the case of a 30-year-old man complaining of acute pain in his right elbow, mild distal paraesthesias, and some motor deficiencies. He was discovered as having a small fusiform swelling of the median nerve. In view of its very small size, shape, and nonspecific MRI signal, it had initially suggested a benign lesion. The diagnosis of epithelioid MPNST was made only at the histopathological examination. This malignant neoplasm recurred locally fourteen months after surgery. In addition to describe the above very rare case, we have reviewed the literature on epithelioid MPNSTs clearly involving deep major nerve trunks. This case serves as a warning that, even in major nerve trunks, tiny lesions may in reality be early intraneural MPNSTs which, due to their deep location, must be treated adequately with wide margin surgery since the resection margin status represents one of the major parameters influencing the local control of disease and its clinical outcome.

[Case report of a subcutaneous peripheral primitive neuroectodermal tumor]

Peripheral primitive neuroectodermal tumors - also known as Ewing sarcomas - are a rare type of malignant tumor the histology of which characteristically reveals the presence of small round cells. Typically, t(11;22) translocation is observed. We describe the case of a 45-year-old man with a subcutaneous peripheral primitive neuroectodermal tumor in which the t(11;22) translocation was detected. He was satisfactorily treated with surgery and radiotherapy.

Concurrent epithelioid malignant peripheral nerve sheath tumor and papillary thyroid carcinoma in the treated field of Hodgkin's disease

BACKGROUND

Simultaneous malignancies in the field of radiation for Hodgkin's disease is an extremely rare event. A unique case of concurrent thyroid and neck mass in the postirradiation field of a young patient with Hodgkin's disease is presented.

METHODS AND RESULTS

Thyroidectomy and excision biopsy of the neck mass were performed. A 1.5-cm papillary thyroid carcinoma was identified in thyroidectomy and an initial diagnosis of undifferentiated malignant neoplasm was rendered on the neck mass biopsy. Subsequent surgical excision of the neck mass and immunohistochemical analysis revealed malignant peripheral nerve sheath tumor.

CONCLUSION

Concurrent malignancies in the field of treatment of Hodgkin's disease may occur. Rare malignancies including malignant peripheral nerve sheath tumor may be encountered along with the more common papillary thyroid carcinoma.

Plexiform Epithelioid Schwannoma:

Epithelioid schwannoma is rare but may pose a challenge in histopathologic diagnosis. In the present report, we describe a plexiform variant of epithelioid schwannoma in the skin of the breast of a 47-year-old woman.

Myxopapillary ependymoma of the posterior mediastinum

A left paravertebral mass discovered incidentally on routine examination in a 39-year-old woman is described. Computerized tomography studies revealed a 7 x 6 cm, well circumscribed, noncalcified soft tissue mass with lobular borders abutting the left inferior pulmonary vein and descending aorta. It was not possible to determine the exact anatomic location of the mass based on the imaging studies as both peripheral lung tumors and posterior mediastinal lesions may exhibit the imaging findings described here. At thoracotomy, the mass was seen to be well circumscribed, focally attached to the pleura but without involvement of lung parenchyma, and situated in the left posterior mediastinum. On histological examination, the lesion showed the classical features of myxopapillary ependymoma. Immunohistochemical studies confirmed this impression by demonstrating strong positivity of the tumor cells for S-100 protein, glial fibrillary acidic protein, and CD99 and negative staining with other differentiation markers. A review of the literature with a discussion of the histologic and radiologic differential diagnosis of these lesions is presented.

Epithelioid malignant peripheral nerve sheath tumor involving maxillary sinus

We present a case of epithelioid malignant peripheral nerve sheath tumor (MPNST) located in the maxillary sinus region in a young man. The clinical history was short, but at admission the neoplastic infiltration was so extensive that only diagnostic biopsy was performed. The patient received palliative treatment and died 6 months later. Histologically, the neoplasm had a predominant epithelioid component. Neoplastic tissue was vimentin, S-100, Cam 5.2 and neuron-specific enolase positive. P53 protein reaction was found in 6% of the cells and the proliferation index assessed with Ki-67 was 52%. An appropriate immunohistochemical panel was essential for the final diagnosis of this epithelioid malignant tumor, with the location rather unusual for MPNST.

Malignant schwannoma of the upper mediastinum originating from the vagus nerve

BACKGROUND

Malignant schwannoma of the upper mediastinum originating from the vagus nerve is extremely rare.

CASE PRESENTATION

A 46-year-old female was admitted for a left cervical mass which was associated with both hoarseness and Horner's syndrome. Chest computed tomography showed a mass extending from the left upper mediastinum to the left supraclavicular area. A fine needle aspiration cytological examination suggested primary lung cancer stage IIIB large cell carcinoma. After administering induction chemo-radiotherapy, a complete surgical resection was performed. The tumor was found to involve both the left vagus nerve and the left sympathetic nerve. Histological examination of the resected specimen revealed the tumor to be malignant schwannoma.

CONCLUSION

Despite incorrect preoperative diagnosis, the multimodality treatment administered in this case, including induction chemo-radiotherapy and surgery, proved to be effective.

Benign Epithelioid Peripheral Nerve Sheath Tumors of the Soft Tissues

Benign epithelioid peripheral nerve sheath tumors (BEPNSTs) have not been fully characterized, and their relationship to conventional schwannoma and neurofibroma has not been satisfactorily established. Herein, we detail the clinicopathologic features of 33 examples of BEPNST. The study included 22 females and 11 males ranging in age from 2 to 68 years (median, 31.5 years). Only one patient probably has neurofibromatosis type 1. The tumors were predominantly dermal/subcutaneous in location (85%) and involved the lower limb (n=15), upper limb (n=11), trunk (n=4), and head/neck (n=3). The lesions ranged in size from 0.3 to 6.8 cm (median, 1.1 cm). Microscopically, the tumors were generally well-circumscribed, uninodular, or multinodular masses. Twenty-six lesions were encapsulated. Tumors consisted of trabeculae, loosely arranged nodules, and cohesive nests of epithelioid tumor cells immersed in collagenous, myxohyaline, or chiefly myxoid stroma. A bland spindled cell component comprising 5% to 40% of the tumor was noted in 15 cases. Mitotic activity ranged from 0 to 6 mitoses/50 high power fields (mean, 1.5 mitoses/50 high power fields) with no abnormal division figures identified. Five lesions were considered atypical based on presence of focal nuclear/nucleolar enlargement and hyperchromasia. Immunohistochemical reactivity for Schwann cell-related markers in tumor cells included S-100 protein (20 of 20 cases), collagen type IV (10 of 10), laminin (8 of 8), nerve growth factor receptor, p75(7 of 8), CD57 (6 of 9), and glial fibrillary acidic protein (8 of 15). CD34-positive fibroblast-like cells were identified in all 12 neoplasms tested. Anti-epithelial membrane antigen highlighted perineurial cells in 9 of the 11 encapsulated tumors. Anti-neurofilament protein did not identify intralesional neuraxons in the 10 tumors evaluated. Eighteen tumors were subtyped as epithelioid neurofibromas. The remaining 15 cases showed some histologic features suggestive of schwannoma, but their uniform cellularity, absence of nuclear palisading, and presence of a significant CD34-positive spindled cell population in 5 cases led to their classification as "BEPNST of indeterminate histogenesis." Evaluation for loss of heterozygosity in 2 cases demonstrated deletion of genetic material on chromosome 22q and 17q involving NF2 and NF1 loci. However, sequencing of NF2 coding sequences revealed no mutations. Follow-up for 18 patients (median interval, 13.5 years), including 4 patients with tumors exhibiting cytologic atypia, revealed a nondestructive recurrence or persistent disease in 3 patients whose tumors lacked atypia, but no evidence of metastatic spread or tumor-related death. BEPNSTs are usually small neoplasms located in superficial soft tissue and have an excellent prognosis after complete local excision. Accurate subclassification of some of these lesions is difficult based on currently available techniques.

Low grade malignant peripheral nerve sheath tumour: varied cytological and histological patterns

BACKGROUND

A small number of malignant peripheral nerve sheath tumours (MPNSTs) are low grade, and the nature of these low grade tumours has never been systematically assessed.

AIMS

To describe the clinicopathological, immunohistochemical, and ultrastructural features of low grade MPNST and to discuss the main differential diagnoses.

METHODS

Four cases of low grade MPNST were studied, including one coexistent with neurofibromatosis type 1. The tumours were analysed with respect to nuclear atypia, cellularity, nuclear enlargement, hyperchromasia, mitotic rate, and necrosis. Immunohistochemistry was performed by standard techniques, and an ultrastructural study was performed on one tumour.

RESULTS

The ages of the patients ranged from 32 to 72 years (mean, 58). Two were male and two were female. Three tumours occurred in the deep tissue, including one in the retroperitoneum, and one was located in the dermal and subcutaneous tissue. The maximum diameters of the tumours ranged from 3.5 to 8.0 cm. Microscopically, all tumours showed moderate hypercellularity, an increased nuclear to cytoplasmic ratio, and hyperchromasia, but exhibited varied growth patterns, including those that were atypical neurofibroma-like, low grade fibromyxoid sarcoma-like, low grade epithelioid, and haemangiopericytoma-like. All tumours showed immunoreactivity for S-100 protein and vimentin.

CONCLUSIONS

These findings suggest that careful clinical and histological evaluation, along with S-100 protein immunostaining, are essential for the accurate diagnosis of low grade MPNST.

Subcutaneous malignant epithelioid schwannoma with cartilaginous differentiation

BACKGROUND

Malignant epithelioid schwannoma is a rare tumor. The aim of this study is to describe a case of subcutaneous malignant epithelioid schwannoma with cartilaginous differentiation.

METHODS

Histological, immunohistochemical, and ultrastructural examinations were performed on a tumor that arose on the back of a 37-year-old woman.

RESULTS

Histologically, the tumor predominantly consisted of small, round or polygonal cells arranged in cords or nests. Immunohistochemical study revealed that the tumors cells were positive for vimentin, S-100 protein, glial fibrillary acidic protein and neuron specific enolase. The cells were negative for HMB-45, keratin, epithelial membrane antigen, and CAM5.2. Electron microscopic study showed closely associated cells with undifferentiated features. The cells were devoid of external laminae and cellular junctions.

CONCLUSION

Malignant epithelioid schwannoma should be pathologically differentiated from other epithelioid tumors with cartilaginous elements.

Schwannomas in the colon and rectum: a clinicopathologic and immunohistochemical study of 20 cases

Schwannomas of the colon and rectum are uncommon and incompletely characterized tumors, and only a small number of cases have been reported. This study was undertaken to determine the clinicopathologic profile of such tumors. A total of 20 colorectal schwannomas were identified and analyzed in a review of 600 mesenchymal tumors of the colon and rectum from the files of the Armed Forces Institute of Pathology. The schwannomas occurred equally in men (n = 9) and women (n = 11) in a wide age range (18-87 years; median age 65 years). The most common location was cecum (n = 7), followed by sigmoid and rectosigmoid (n = 6), transverse colon (n = 3), descending colon (n = 2), and rectum (n = 1); the location of one tumor had not been specified. The tumors commonly presented as polypoid intraluminal lesions, often with mucosal ulceration. Rectal bleeding, colonic obstruction, and abdominal pain were the most common presenting symptoms. The most common histologic variant (n = 15) was a spindle cell schwannoma with a trabecular pattern and vague or no Verocay bodies. These tumors ranged from 0.5 to 5.5 cm in diameter. A lymphoid cuff with germinal centers typically surrounded these tumors and focal nuclear atypia was often present, but mitotic activity never exceeded 5 per 50 HPF. All four epithelioid schwannomas occurred in the descending colon or sigmoid, three of them as small submucosal tumors. There was one plexiform schwannoma in the sigmoid composed of multiple nodules of prominently palisading schwann cells similar to those seen in conventional soft tissue schwannomas. All tumors studied were strongly positive for S-100 protein and also for low affinity nerve growth factor receptor (p75), collagen IV, and GFAP. Three tumors had CD34-positive cells, but all were negative for CD117 (KIT), neurofilament proteins, smooth muscle actin, and desmin. The percentage of MIB-1-positive cells was usually less than 1% and never higher than 3%. Colorectal schwannomas behaved in a benign fashion with no evidence of aggressive behavior or connection with neurofibromatosis 1 or 2, based on follow-up information on 18 patients.

Sclerosing epithelioid fibrosarcoma: a study of 16 cases and confirmation of a clinicopathologically distinct tumor

Sclerosing epithelioid fibrosarcoma (SEF) is an uncommon tumor of deep soft tissues, originally described in 1995 by Meis-Kindblom et al. In the current study, the authors identified 16 cases of SEF in the pathology files of their institutions and studied their pathologic features and disease course. The group consisted of six male and 10 female patients (age range, 14-55 years; mean age, 40 years), and the tumors were located in a limb or limb girdle (n = 7), base of the penis (n = 1), back or chest wall (n = 3), and head and neck (n = 5). Tumor size ranged from 3.7 to 22 cm (mean, 8.9 cm). Histologically, the SEFs were composed predominantly of small to moderate-size round to ovoid, relatively uniform cells, often with clear cytoplasm, embedded in a hyalinized fibrous stroma. The only consistent immunohistochemical finding was a strong, diffuse reactivity of tumor cells for vimentin. Ultrastructural analysis performed in eight cases confirmed their fibroblastic nature. Bone invasion and tumor necrosis, features not reported before, were found in six cases each. Treatment consisted of intralesional excision (n = 2), attempted wide local excision (n = 11), and amputation (n = 3), with either adjuvant radiation therapy (n = 9) or chemotherapy (n = 3). Follow-up of at least 1 year in 14 cases revealed persistent disease or local recurrence in seven patients (50%), and distant metastasis in 12 patients (86%). Eight patients (57%) died of disease 16 to 86 months after diagnosis. Five patients were alive with disease as of last follow-up. SEF shares some pathologic features with two other fibrosing fibrosarcomas, low-grade fibromyxoid sarcoma and hyalinizing spindle cell tumor with giant rosettes, but in the authors' experience behaves clinically as a fully malignant sarcoma.

Fine-needle aspiration cytology and core biopsy of malignant peripheral nerve sheath tumor of the uterus: a case report

Malignant peripheral nerve sheath tumor (MPNST) is an uncommon mesenchymal neoplasm of neural origin. MPNST arising in the uterus is extremely rare. Its histologic appearance on this anatomical location has been only rarely reported. A 62-yr-old woman with a previous history of partial hysterectomy presented with a large pelvic mass in the uterine stump. Fine-needle aspiration (FNA) and core biopsy were obtained under ultrasonographic guidance, and the diagnosis of MPNST was established. The cytologic and histologic findings were consistent with a spindle-cell neoplasm suggestive of MPNST. The tumor cells were focally positive for S-100 protein immunostain, thus providing further support for the neoplasm's nerve sheath differentiation. The patient had no history of von Recklinghausen's disease. Resection of the mass confirmed the diagnosis of MPNST. To our knowledge, the FNA cytology of MPNST in this unusual location has not been previously reported. FNA cytology, along with core biopsy and immunochemistry, is a reliable tool in the diagnosis of MPNST.

Primary malignant schwannoma of the uterine cervix: a case report and literature review

Primary malignant schwannomas are a very rare neural sheath tumor. A case of primary epithelioid-type malignant schwannoma of the uterine cervix in a 65-year-old woman is presented. This tumor is the first epithelioid malignant schwannoma documented within gynecologic tissues. Only two other cases of primary malignant schwannoma of the uterine cervix have been reported, and these cases are reviewed.

Extraskeletal myxoid chondrosarcoma: a reappraisal of its morphologic spectrum and prognostic factors based on 117 cases

Extraskeletal myxoid chondrosarcoma (EMC), a phenotypically and genotypically distinctive entity, has generally been viewed as a low-grade sarcoma. No studies regarding clinical and morphologic prognostic factors have been performed on a large series of cases with long-term follow-up because of the rarity and protracted clinical course of EMC. The clinical, morphologic, and immunohistochemical features of 117 previously unreported cases were studied and statistically analyzed. The male-to-female ratio was 2:1. The median patient age was 52 years (range, 6-89 years), and the median tumor size was 7 cm (range, 1.1-25 cm). All tumors occurred within the deep subcutis or deeper soft tissues, with 80% occurring in the proximal extremities or limb girdles and 20% in the trunk. Most initial tumor excisions were intralesional or marginal. Follow-up information was available in 99 cases (median, 9 years: range, 2 months-22 years). Forty-eight patients were disease-free, and 41 patients had evidence of disease (18 of these had died of disease). Ten additional patients survived, but their disease status was unknown. There were local recurrences in 40 (48%) of 83 patients, 23 (58%) of whom had multiple local recurrences. Metastases occurred in 35 (46%) of 76 patients. The estimated 5-, 10-, and 15-year survival rates were 90%, 70%, and 60%, respectively. All cases had histologic features characteristic of classical EMC, at least focally. Cellular foci devoid of myxoid matrix and reminiscent of chondroblastoma, Ewing's sarcoma, monophasic and poorly differentiated synovial sarcoma, fibrosarcoma, and rhabdoid tumor were identified in 29% cases. Older patient age, larger tumor size, and tumor location in the proximal extremity or limb girdle were adverse prognostic factors identified by multivariate analysis. Metastasis also adversely affected survival, although local recurrence did not. This study shows that EMC has a unique clinical course, including a high rate of local recurrence, prolonged survival after metastasis in some cases, and eventually a high rate of death due to tumor. These features distinguish EMC from low-grade sarcomas. This study shows that histologic grading is of no prognostic value in EMC because prognosis is dictated primarily by certain clinical features. Histologic recognition of classical EMC and cellular and solid, nonmyxoid variants is important, however, in view of EMC's distinctive biologic behavior.

Primary intraosseous malignant peripheral nerve sheath tumor: a case report and review of the literature

Primary intraosseous malignant peripheral nerve sheath tumors (MPNST) are exceptionally rare; the case reported here represents the first documented example occurring in the spinal column. The tumor arose in the second cervical vertebra of a forty year old woman of Asian origin. She had no stigmata of von Recklinghausen's disease (VRD). Plain radiographs and magnetic resonance imaging showed an osteolytic lesion within the expanded body of the vertebra. Histology revealed spindle-shaped tumor cells with nuclei showing pleomorphism, pallisading and mitotic activity. The cells stained positively for S-100 protein. The patient underwent stabilisation of the cervical spine and tumor excision as a two-stage procedure. She died of pulmonary metastases one year later. We have reviewed the literature on the pathology of these tumors.

Benign epithelioid schwannoma

Benign schwannoma (neurilemoma) has various morphologic patterns that may cause problems in differential diagnosis. Although an epithelioid variant of malignant schwannoma simulating carcinoma and melanoma is well recognized, a benign counterpart has not yet been defined. In the current study, we describe five cases of benign epithelioid schwannoma that were in the subcutis (four cases) and the neck of the urinary bladder (one case). The tumors occurred in adults 28-73 years of age, were 1-4.5 cm in diameter, were well circumscribed and cellular, and were composed of epithelioid cells arranged in cords and nests. The benign nature of the lesions was evident by a constellation of features, including small size, sharp circumscription, bland morphology, low proliferative activity (four of five had < or =1% Ki67 immunostaining), and a benign clinical course after either marginal or intralesional excision. All cases had some features of classic schwannoma light microscopically and a high degree of Schwann cell differentiation both ultrastructurally and immunohistochemically. The recognition of benign epithelioid schwannoma is important because it may be misinterpreted as a malignant neuroectodermal, mesenchymal, epithelioid, or melanocytic tumor.

Canine peripheral nerve sheath tumor with eosinophilic cytoplasmic globules

A 13-year-old male Shetland Sheepdog had a subcutaneous tumor in the left brachium. The tumor was removed and recurred several times at 5, 13, 16, 22, and 31 months after the initial presentation. Histologically, the removed nodules from the fourth resection were composed of neoplastic proliferation of round to fusiform cells, which possessed eosinophilic globules in their cytoplasm. The globules were periodic acid-Schiff positive and diastase resistant. Positive reactions for acid phosphatase were observed in the cytoplasm of the tumor cells. Ultrastructurally, these globules consisted of membrane-bound, dense structures containing dense granules, lucent vacuoles, and homogeneous materials. The recurrent tumors removed at the fifth resection consisted of spindle cell proliferation arranged in interlacing fascicles with wavy nuclei and containing a small number of cells with cytoplasmic globules. The tumor cells were immunoreactive to vimentin, S-100 protein, myelin basic protein, and neuron-specific enolase. The tumor was diagnosed as a peripheral nerve sheath tumor with eosinophilic cytoplasmic globules. These findings are unique for the histogenesis of granular cell tumors.

Neoplasms with neural differentiation: a review. Part II: Malignant neoplasms

Malignant peripheral nerve sheath tumors (MPNSTs) encompass a wide and unusual group of neoplasms with features of neural differentiation. They most commonly present as spindle cell neoplasms and it can be difficult to differentiate them from other spindle cell neoplasms such as leiomyosarcomas, fibrosarcomas and synovial sarcomas. Strict criteria need to be applied in order to make the diagnosis of MPNSTs. Helpful features include contiguity with a nerve or an association with von Recklinghausen disease. The use of immunohistochemical stains may also help to confirm the diagnosis. Markers such as S-100 protein, neurofilament, epithelial membrane antigen and Leu-7 (CD57) are frequently used to assess neural differentiation in these neoplasms. In addition to the spindle cell pattern, MPNSTs may also display an epithelioid pattern. Rarely, other elements may be seen including glands in the so-called glandular MPNST or muscle in triton tumors. In more unusual cases cartilage, adipose tissue and even bone are present. Also included in the group of MPNSTs are the peripheral neuroepithelial tumor, neurotropic or desmoplastic melanomas and malignant granular cell tumors. MPNSTs are highly aggressive tumors and should be treated accordingly.

Malignant peripheral nerve sheath tumor of the pleura with epithelial and rhabdomyoblastic differentiation: report of a case clinically simulating mesothelioma

A primary malignant peripheral nerve sheath tumor (MPNST) of the pleura that clinically mimicked a malignant mesothelioma in a 57-year-old man is described. Histologically, the tumor had features similar to those described in cases of the so-called epithelioid MPNST. A unique finding in this case was the demonstration of keratin expression in the epithelioid component of the tumor, as well as the presence of rhabdomyoblasts. This is the first example of an MPNST with heterologous elements arising in the pleura. Immunohistochemical and ultrastructural studies were important in differentiating this tumor from other malignancies with sarcomatoid and epithelioid features involving the pleura.