Epidermal growth factor receptor is not amplified in schwannomas

Clinicopathological variables of sporadic schwannomas of peripheral nerve in 291 patients and expression of biologically relevant markers

OBJECTIVE While sporadic peripheral schwannomas (SPSs) are generally well treated with surgery, their biology is not well understood. Consequently, treatment options are limited. The aim of this study was to provide a comprehensive description of SPS. The authors describe clinicopathological features and treatment outcomes of patients harboring these tumors, and they assess expression of biomarkers using a clinically annotated tissue microarray. Together, these data give new insight into the biology and management of SPS. METHODS Patients presenting with a primary SPS between 1993 and 2011 (n = 291) were selected from an institutional registry to construct a clinical database. All patients underwent follow-up, and short- and long-term outcomes were assessed. Expression of relevant biomarkers was assessed using a new tissue microarray (n = 121). RESULTS SPSs were generally large (mean 5.5 cm) and frequently painful at presentation (55%). Most patients were treated with surgery (80%), the majority of whom experienced complete resolution (52%) or improvement (18%) of their symptoms. Tumors that were completely resected (85%) did not recur. Some patients experienced short-term (16%) and long-term (4%) complications postoperatively. Schwannomas expressed higher levels of platelet-derived growth factor receptor-β (2.1) than malignant peripheral nerve sheath tumors (MPNSTs) (1.5, p = 0.004) and neurofibromas (1.33, p = 0.007). Expression of human epidermal growth factor receptor-2 was greater in SPSs (0.91) than in MPNSTs (0.33, p = 0.002) and neurofibromas (0.33, p = 0.026). Epidermal growth factor receptor was expressed in far fewer SPS cells (10%) than in MPNSTs (58%, p < 0.0001) or neurofibromas (37%, p = 0.007). SPSs more frequently expressed cytoplasmic survivin (66% of tumor cells) than normal nerve (46% of cells), but SPS expressed nuclear survivin in fewer tumor cells than in MPNSTs (24% and 50%, respectively; p = 0.018). CONCLUSIONS Complete resection is curative for SPS. Left untreated, however, these tumors can cause significant morbidity, and not all patients are candidates for resection. SPSs express a pattern of biomarkers consistent with the dysregulation of the tumor suppressor merlin observed in neurofibromatosis Type 2-associated schwannomas, suggesting a shared etiology. This SPS pattern is distinct from that of other tumors of the peripheral nerve sheath.

Morphologic and immunohistochemical features of malignant peripheral nerve sheath tumors and cellular schwannomas

Cellular schwannoma is an uncommon, but well-recognized, benign peripheral nerve sheath tumor, which can be misdiagnosed as malignant peripheral nerve sheath tumor. To develop consensus diagnostic criteria for cellular schwannoma, we reviewed 115 malignant peripheral nerve sheath tumor and 26 cellular schwannoma cases from two institutions. Clinical data were retrieved from the electronic medical records, and morphologic features, maximal mitotic counts, Ki67 labeling indices, and immunohistochemical profiles (SOX10, SOX2, p75NTR, p16, p53, EGFR, and neurofibromin) were assessed. Several features distinguish cellular schwannoma from malignant peripheral nerve sheath tumor. First, in contrast to patients with malignant peripheral nerve sheath tumor, no metastases or disease-specific deaths were found in patients with cellular schwannoma. More specifically, 5-year progression-free survival rates were 100 and 18%, and 5-year disease-specific survival rates were 100 and 32% for cellular schwannoma and malignant peripheral nerve sheath tumor, respectively. Second, the presence of Schwannian whorls, a peritumoral capsule, subcapsular lymphocytes, macrophage-rich infiltrates, and the absence of fascicles favored the diagnosis of cellular schwannoma, while the presence of perivascular hypercellularity, tumor herniation into vascular lumens, and necrosis favor malignant peripheral nerve sheath tumor. Third, complete loss of SOX10, neurofibromin or p16 expression, or the presence of EGFR immunoreactivity was specific for malignant peripheral nerve sheath tumor (P<0.001 for each). Expression of p75NTR was observed in 80% of malignant peripheral nerve sheath tumors compared with 31% of cellular schwannomas (P<0.001). Fourth, Ki-67 labeling indices ≥20% were highly predictive of malignant peripheral nerve sheath tumor (87% sensitivity and 96% specificity). Taken together, the combinations of these histopathological and immunohistochemical features provide useful criteria to distinguish between malignant peripheral nerve sheath tumor and cellular schwannoma with high sensitivity and specificity. Additional retrospective and prospective multicenter studies with larger data sets will be required to validate these findings.

Schwannomas and their pathogenesis

Schwannomas may occur spontaneously, or in the context of a familial tumor syndrome such as neurofibromatosis type 2 (NF2), schwannomatosis and Carney's complex. Schwannomas have a variety of morphological appearances, but they behave as World Health Organization (WHO) grade I tumors, and only very rarely undergo malignant transformation. Central to the pathogenesis of these tumors is loss of function of merlin, either by direct genetic change involving the NF2 gene on chromosome 22 or secondarily to merlin inactivation. The genetic pathways and morphological features of schwannomas associated with different genetic syndromes will be discussed. Merlin has multiple functions, including within the nucleus and at the cell membrane, and this review summarizes our current understanding of the mechanisms by which merlin loss is involved in schwannoma pathogenesis, highlighting potential areas for therapeutic intervention.

Microarray analysis of gene expression in vestibular schwannomas reveals SPP1/MET signaling pathway and androgen receptor deregulation

Vestibular schwannomas are benign neoplasms that arise from the vestibular nerve. The hallmark of these tumors is the biallelic inactivation of neurofibromin 2 (NF2). Transcriptomic alterations, such as the neuregulin 1 (NRG1)/ErbB2 pathway, have been described in schwannomas. In this study, we performed a whole transcriptome analysis in 31 vestibular schwannomas and 9 control nerves in the Affymetrix Gene 1.0 ST platform, validated by quantitative real-time PCR (qRT-PCR) using TaqMan Low Density arrays. We performed a mutational analysis of NF2 by PCR/denaturing high-performance liquid chromatography (dHPLC) and multiplex ligation-dependent probe amplification (MLPA), as well as a microsatellite marker analysis of the loss of heterozygosity (LOH) of chromosome 22q. The microarray analysis demonstrated that 1,516 genes were deregulated and 48 of the genes were validated by qRT-PCR. At least 2 genetic hits (allelic loss and/or gene mutation) in NF2 were found in 16 tumors, seven cases showed 1 hit and 8 tumors showed no NF2 alteration. MET and associated genes, such as integrin, alpha 4 (ITGA4)/B6, PLEXNB3/SEMA5 and caveolin-1 (CAV1) showed a clear deregulation in vestibular schwannomas. In addition, androgen receptor (AR) downregulation may denote a hormonal effect or cause in this tumor. Furthermore, the osteopontin gene (SPP1), which is involved in merlin protein degradation, was upregulated, which suggests that this mechanism may also exert a pivotal role in schwannoma merlin depletion. Finally, no major differences were observed among tumors of different size, histological type or NF2 status, which suggests that, at the mRNA level, all schwannomas, regardless of their molecular and clinical characteristics, may share common features that can be used in their treatment.

DNA copy gains of tumor-related genes in vestibular schwannoma

DNA copy gains are a common event in tumor growth. This study determines the gene dosage/amplification of seven tumor-related genes in patients undergoing vestibular schwannoma (VS) surgery and analyzes its clinical implications. Thirty-three patients undergoing surgery for VS were studied. Seven genes (EGFR, ERBB2, ERBB3, ERBB4, MDM2, MDM4, and NMYC) were analyzed by Quantitative real-time PCR. Copy gains were correlated with demographic, clinical and radiological data. Of the 33 samples, 48 % were positive for copy gains in at least one gene. There were no positive samples for gene amplification. A clinical correlation between tumor size and copy gains of ERBB2 was found. Patients with copy gains of this gene had larger tumors measured by diameter (p = 0.027) and volume (p = 0.005). Copy gains of EGFR, ERBB2, ERBB4, and MDM4 were associated with preoperative tinnitus. Contrary to other tumors of the central nervous system, development of VS does not appear to involve gene amplification. However, copy gains of certain tumor-related genes may play a role in the biological behavior of these neoplasms. Our findings support the role of ERBB2 in VS development and growth.

Brain tumors in adults with medically intractable epilepsy

Much of the literature on tumors arising in the setting of chronic epilepsy focuses on children. This study reviewed 1 institution's 141-patient experience with tumors in adults arising in this clinical setting. The majority of tumors (71.6%) arose in the temporal lobe. The most common tumor types encountered included ganglioglioma (n = 38), low-grade fibrillary astrocytoma (n = 24), and low-grade oligodendroglioma (n = 22). Coexistent focal cortical dysplasia (type IA) was identified in 15 cases (10.6%). The largest group of tumors in adults were World Health Organization (WHO) grade II neoplasms compared with WHO grade I tumors in children. Gangliogliomas are the most commonly encountered neoplasms. Coexistent focal cortical dysplasia may be observed in a significant minority of tumors, suggesting a possible developmental origin for some of these neoplasms.

Erlotinib for progressive vestibular schwannoma in neurofibromatosis 2 patients

OBJECTIVE

In vitro treatment of Nf2-deficient cells with epidermal growth factor receptor (EGFR) inhibitors can reduce cellular proliferation. We sought to determine the activity of erlotinib for progressive vestibular schwannoma (VS) associated with neurofibromatosis 2 (NF2).

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Eleven NF2 patients with progressive VS who were poor candidates for standard therapy.

INTERVENTION

Erlotinib 150 mg daily.

MAIN OUTCOME MEASURES

A radiographic response was defined as >or= 20% decrease in tumor volume compared with baseline. A hearing response was defined as a statistically significant increase in word recognition score (WRS) compared with baseline; a minor hearing response was defined as a 10 dB improvement in pure-tone average with stable WRS.

RESULTS

: Before treatment, the median and mean annual volumetric growth rate for 11 index VS were 26% and 46%, respectively. Among 10 evaluable patients, the median time-to-tumor progression was 9.2 months. Three patients with stable disease experienced maximum tumor shrinkage of 4%, 13%, and 14%. Nine patients underwent audiologic evaluations. One experienced a transient hearing response, 2 experienced minor hearing responses, 3 remained stable, and 2 developed progressive hearing loss. The median time-to-progressive hearing loss was 9.2 months and to either tumor growth or progressive hearing loss was 7.1 months. Adverse treatment effects included mild-to-moderate rash, diarrhea, and hair thinning, with 2 episodes of grade 3 toxicity.

CONCLUSION

Erlotinib treatment was not associated with radiographic or hearing responses in NF2 patients with progressive VS. Because a subset of patients experienced prolonged stable disease, time-to-progression may be more appropriate than radiographic or hearing response for anti-EGFR agents in NF2-associated VS.

Tumours arising in the setting of paediatric chronic epilepsy

BACKGROUND

Along with malformations of cortical development or cortical dysplasia, hippocampal sclerosis, and remote ischaemic damage, tumours are among the more commonly identifiable causes of medically intractable seizures in paediatric age patients. This study reviews one institution's 20 year experience with tumours arising in this clinical setting.

METHODS

Retrospective review of 129 paediatric patients [less than 19 years of age, 65 females (50.4%)] with tumours and medically intractable seizures encountered during a 20 year period of time (1989-2009). Using the most recent World Health Organization (WHO) classification of brain tumours, tumour type and grade were assessed.

RESULTS

The most common sites of origin included temporal lobe (n = 77, 59.7%), parietal lobe (n = 20, 15.5%), and frontal lobe (n = 15, 11.6%). WHO grade included 73 (56.6%) grade I tumours, 32 (24.8%) grade II tumours, and 18 (14%) grade I/II tumours. In six cases (4.7%), a WHO grade was not associated with mass. Tumour types included: ganglioglioma (n = 48, 37.2%), dysembryoplastic neuroepithelial tumour (n = 17, 13.2%), low grade astrocytoma (n = 15, 11.6%), low grade mixed glioma (n = 8, 6.2%), low grade oligodendroglioma (n = 5, 3.9%), meningioangiomatosis (n = 4, 3.1%) angiocentric glioma (n = 3, 2.3%), and dysembryoplastic neuroepithelial tumour/ganglioglioma composite tumour (n = 3, 2.3%). Less frequently observed lesions (n = 1 or 2) included pilocytic astrocytoma, protoplasmic astrocytoma, pleomorphic xanthoastrocytoma, and glioneuronal hamartoma. In 18 cases, distinction between low grade glioma and low grade glioneuronal tumour could not be definitively made. Coexisting malformation of cortical development/cortical dysplasia was noted in 29.8% of evaluable cases. In four tumours, coexistent hippocampal sclerosis was identified. Ki-67 labelling indices were less than 5% in all (n = 51) cases assessed. Of 25 tumours evaluated for chromosome 1p status, only one low grade mixed glioma demonstrated evidence of deletion; only one of 22 evaluated tumours (a low grade mixed glioma) showed evidence of chromosome 19q deletion.

CONCLUSION

Collectively, WHO grade I glioneuronal tumours account for slightly more than half of all neoplasms which cause intractable epilepsy in paediatric patients. A significant minority of tumours (n = 18, 14%) were difficult to definitively classify as glioma versus glioneuronal tumour, due to extent of sampling. Coexistent pathologies including malformation of cortical development/cortical dysplasia may be observed in a significant minority of tumours, suggesting a possible developmental origin for some tumours arising in this setting.