Tim-Rasmus Kiehl

Primary frozen section diagnosis by robotic microscopy and virtual slide telepathology: the University Health Network experience.

Although telepathology (TP) has not been widely implemented for primary frozen section diagnoses, interest in its use is growing as we move into an age of increasing subspecialization and centralization of pathology services. University Health Network is a 3-site academic institution in downtown Toronto. The pathology department is consolidated at its Toronto General Hospital (TGH) site. The Toronto Western Hospital (TWH), located 1 mile to west of TGH, has no on-site pathologist, and generates 5 to 10 frozen section cases per week. More than 95% of these frozen sections are submitted by neurosurgeons, in most cases to confirm the presence of lesional tissue and establish a tissue diagnosis. In 2004, we implemented a robotic microscopy (RM) TP system to cover these frozen sections. In 2006, we changed to a virtual slide (VS) TP system. Between November 2004 and September 2006, 350 primary frozen section diagnoses were made by RM. An additional 633 have been reported by VS TP since October 2006, giving a total of 983 frozen sections from 790 patients. Of these cases, 88% have been single specimens with total turnaround times averaging 19.98 and 15.68 minutes per case by RM and VS TP, respectively (P < .0001). Pathologists required an average of 9.65 minutes to review a slide by RM. This decreased 4-fold to 2.25 minutes after the change to VS TP (P < .00001). Diagnostic accuracy has been 98% with both modalities, and our overall deferral rate has been 7.7%. Midcase technical failure has occurred in 3 cases (0.3%) resulting in a delay, where a pathologist went to TWH to report the frozen section. Discrepant cases have typically involved minor interpretive errors related to tumor type. None of our discrepant TP diagnoses has had clinical impact to date. We have found TP to be reliable and accurate for frozen section diagnoses. In addition to its superior speed and image quality, the VS approach readily facilitates consultation with colleagues on difficult cases. As a result, there has been greater overall pathologist satisfaction with VS TP.

Association Between Early-Onset Parkinson Disease and 22q11.2 Deletion Syndrome: Identification of a Novel Genetic Form of Parkinson Disease and Its Clinical Implications

IMPORTANCE Clinical case reports of parkinsonism co-occurring with hemizygous 22q11.2 deletions and the associated multisystem syndrome, 22q11.2 deletion syndrome (22q11.2DS), suggest that 22q11.2 deletions may lead to increased risk of early-onset Parkinson disease (PD). The frequency of PD and its neuropathological presentation remain unknown in this common genetic condition. OBJECTIVE To evaluate a possible association between 22q11.2 deletions and PD. DESIGN, SETTING, AND PARTICIPANTS An observational study of the occurrence of PD in the worlds largest cohort of well-characterized adults with a molecularly confirmed diagnosis of 22q11.2DS (n = 159 [6 with postmortem tissue]; age range, 18.1-68.6 years) was conducted in Toronto, Ontario, Canada. Rare postmortem brain tissue from individuals with 22q11.2DS and a clinical history of PD was investigated for neurodegenerative changes and compared with that from individuals with no history of a movement disorder. MAIN OUTCOMES AND MEASURES A clinical diagnosis of PD made by a neurologist and neuropathological features of PD. RESULTS Adults with 22q11.2DS had a significantly elevated occurrence of PD compared with standard population estimates (standardized morbidity ratio = 69.7; 95% CI, 19.0-178.5). All cases showed early onset and typical PD symptom pattern, treatment response, and course. All were negative for family history of PD and known pathogenic PD-related mutations. The common use of antipsychotics in patients with 22q11.2DS to manage associated psychiatric symptoms delayed diagnosis of PD by up to 10 years. Postmortem brain tissue revealed classic loss of midbrain dopaminergic neurons in all 3 postmortem 22q11.2DS-PD cases. Typical α-synuclein-positive Lewy bodies were present in the expected distribution in 2 cases but absent in another. CONCLUSIONS AND RELEVANCE These findings suggest that 22q11.2 deletions represent a novel genetic risk factor for early-onset PD with variable neuropathological presentation reminiscent of LRRK2-associated PD neuropathology. Individuals with early-onset PD and classic features of 22q11.2DS should be considered for genetic testing, and those with a known 22q11.2 deletion should be monitored for the development of parkinsonian symptoms. Molecular studies of the implicated genes, including DGCR8, may help shed light on the underlying pathophysiology of PD in 22q11.2DS and idiopathic PD.

Neuropathologic Features in Adults with 22q11.2 Deletion Syndrome

The 22q11.2 deletion syndrome (22qDS) is the most common microdeletion syndrome in humans. Its multisystem manifestations include congenital anomalies and neuropsychiatric disorders such as schizophrenia. Structural neuroimaging shows various abnormalities, but no postmortem brain studies exist. We report neuropathologic findings in 3 individuals from a cohort of 100 adults with a confirmed 22q11.2 deletion. All 3 had schizophrenia. Postmortem examination of Case 1, a 44-year-old male, revealed bilateral periventricular nodular heterotopia in the frontal lobes and ectopic neurons scattered throughout the frontal white matter. Cases 2 (male, aged 22 years) and 3 (female, 52 years) showed no evidence of migration abnormalities, but both had extensive astrocytic gliosis and focal collections of macrophages in the cerebral white matter, suggestive of cerebrovascular pathology. Review of magnetic resonance imaging findings available for 66 other subjects in the cohort revealed polymicrogyria in one and right cerebellar disorganization in another of the 26 subjects with schizophrenia. The results support previous neuroimaging reports suggesting that neuronal migration abnormalities may be a feature of 22qDS. Both early developmental brain abnormalities and fetal and later microvascular pathology may play a role in the pathogenesis of the neuropsychiatric phenotype of 22qDS, including white matter abnormalities and schizophrenia.

Human neuropathological and animal model evidence supporting a role for Fas-mediated apoptosis and inflammation in cervical spondylotic myelopathy

Although cervical spondylotic myelopathy is a common cause of chronic spinal cord dysfunction in humans, little is known about the molecular mechanisms underlying the progressive neural degeneration characterized by this condition. Based on animal models of cervical spondylotic myelopathy and traumatic spinal cord injury, we hypothesized that Fas-mediated apoptosis and inflammation may play an important role in the pathobiology of human cervical spondylotic myelopathy. We further hypothesized that neutralization of the Fas ligand using a function-blocking antibody would reduce cell death, attenuate inflammation, promote axonal repair and enhance functional neurological outcomes in animal models of cervical spondylotic myelopathy. We examined molecular changes in post-mortem human spinal cord tissue from eight patients with cervical spondylotic myelopathy and four control cases. Complementary studies were conducted using a mouse model of cervical spondylotic myelopathy (twy/twy mice that develop spontaneous cord compression at C2-C3). We observed Fas-mediated apoptosis of neurons and oligodendrocytes and an increase in inflammatory cells in the compressed spinal cords of patients with cervical spondylotic myelopathy. Furthermore, neutralization of Fas ligand with a function-blocking antibody in twy/twy mice reduced neural inflammation at the lesion mediated by macrophages and activated microglia, glial scar formation and caspase-9 activation. It was also associated with increased expression of Bcl-2 and promoted dramatic functional neurological recovery. Our data demonstrate, for the first time in humans, the potential contribution of Fas-mediated cell death and inflammation to the pathobiology of cervical spondylotic myelopathy. Complementary data in a murine model of cervical spondylotic myelopathy further suggest that targeting the Fas death receptor pathway is a viable neuroprotective strategy to attenuate neural degeneration and optimize neurological recovery in cervical spondylotic myelopathy. Our findings highlight the possibility of medical treatments for cervical spondylotic myelopathy that are complementary to surgical decompression.

Radiation-induced vertebral compression fracture following spine stereotactic radiosurgery: clinicopathological correlation

Spine stereotactic radiosurgery (SRS) is increasingly being used to treat metastatic spinal tumors. As the experience matures, high rates of vertebral compression fracture (VCF) are being observed. What is unknown is the mechanism of action; it has been postulated but not confirmed that radiation itself is a contributing factor. This case report describes 2 patients who were treated with spine SRS who subsequently developed signal changes on MRI consistent with tumor progression and VCF; however, biopsy confirmed a diagnosis of radiation-induced necrosis in 1 patient and fibrosis in the other. Radionecrosis is a rare and serious side effect of high-dose radiation therapy and represents a diagnostic challenge, as the authors have learned from years of experience with brain SRS. These cases highlight the issues in the new era of spine SRS with respect to relying on imaging alone as a means of determining true tumor progression. In those scenarios in which it is unclear based on imaging if true tumor progression has occurred, the authors recommend biopsy to rule out radiation-induced effects within the bone prior to initiating salvage therapies.

Molecular evolution of a neurofibroma to malignant peripheral nerve sheath tumor (MPNST) in an NF1 patient: correlation between histopathological, clinical and molecular findings

ObjectiveNeurofibromatosis type 1 (NF1) patients have a 13% risk of developing a malignant peripheral nerve sheath tumor (MPNST). Many MPNSTs are histopathologically complex, with regions exhibiting features of the original benign plexiform neurofibroma (PNF), of an atypical PNF, or of MPNST showing varying degrees of de-differentiation. This study analyzed the genetic alterations associated with this pathological heterogeneity in order to identify the genetic processes involved in transformation from a benign to an aggressive malignant tumor.MethodsA histological and molecular analysis of a single MPNST tumor that was subdivided into three histopathologically distinct regions, a benign PNF (region 1), an atypical PNF (region 2), and a high-grade MPNST (region 3), was carried out. Tumor DNA from each region was analyzed in conjunction with the patient’s lymphocyte DNA. Somatic mutation analyses included loss-of heterozygosity (LOH), MLPA analysis, NF1 gene sequencing, and a microarray comparative genomic hybridisation (array CGH) analysis.ResultsThe patient had a germline NF1 splice-site mutation. The NF1-associated LOH analysis found that LOH increased in the three tumor areas, with 9, 42, and 97% LOH evident in regions 1, 2, and 3, respectively. Additional genetic changes, including losses of TP53, RB1, CDKN2A, and of several oncogenes and cell-cycle genes, were found only in the malignant MPNST (region 3). Array CGH also identified genomic gains and losses in DNA from region 3.DiscussionThis is the first study that correlates the histological and molecular changes associated with MPNST development, confirming the significant cellular and genetic heterogeneity that poses both diagnostic and therapeutic challenges.

Potential role of 18fluorodeoxyglucose-positron emission tomography/computed tomography in differentiating benign neurofibroma from malignant peripheral nerve sheath tumor associated with neurofibromatosis 1.

OBJECTIVEBenign plexiform neurofibromas (PNfib), especially those occurring in patients with neurofibromatosis type 1, are at a significant risk of progressing to a malignant peripheral nerve sheath tumor (MPNST). Early diagnosis, followed by radical surgery and adjuvant radiation to maintain local tumor control, is of critical importance to prevent metastasis and subsequent mortality from MPNSTs. However, early diagnosis is hampered by the sensitivity of current imaging modalities such as computed tomography (CT) or magnetic resonance imaging to reliably detect this malignant transformation, which can occur heterogeneously in a PNfib to a MPNST. 18Fluorodeoxyglucose (18FDG)–positron emission tomography (PET) is linked to metabolism and proliferation of tissues and has been widely used in oncology including PNSTs. 18FDG-PET/CT has the added advantage of fusing metabolic and anatomic imaging data sets. METHODSIn this prospective study, 9 neurofibromatosis type 1–associated PNfibs suspected to have undergone transformation to an MPNST were preoperatively evaluated by 18FDG-PET/CT and magnetic resonance imaging. A detailed histological evaluation correlated the average and regional standard uptake value (SUV) from the 18FDG-PET/CT to grade of malignancy of the suspected MPNST. RESULTSImaging from 18FDG-PET/CT and associated SUV of the suspected MPNSTs demonstrated either a homogeneous or a heterogeneous pattern. Stratification of the maximal SUV to low (<4.0), intermediate (4.0–7.0), or high (>7.0) correlated to the proliferative index (Ki-67) and grade of MPNST. A maximal SUV of more than 7.0 was closely correlated to a focus of malignant transformation. CONCLUSIONThis study, on a limited number of cases, demonstrates the potential use of 18FDG-PET/CT to augment management of PNfibs, especially in the context of neurofibromatosis type 1, which is characterized by multiple tumors. The addition of CT anatomic imaging to 18FGD-PET can facilitate targeting biopsies to metabolic hot spots, to further augment diagnostic sensitivity. Much larger numbers of MPNSTs, which can only be accrued in a collaborative manner among institutions, are required to further assess the specificity and sensitivity of 18FDG-PET/CT in the diagnosis of MPNSTs.

Subacute CNS demyelination after treatment with nivolumab for melanoma

Checkpoint blockade carries risks of immune-related adverse effects, but frequency and severity are unknown. A patient is described who received anti–CTLA-4 (ipilimumab), and then anti–PD-1 (nivolumab). The patient developed lethal subacute and progressive CNS demyelination. Immunotherapy with monoclonal antibodies targeting cytotoxic T-lymphocyte antigen 4 (CTLA-4) or programmed cell death 1 (PD-1) has improved the survival of patients with metastatic melanoma. These agents carry a certain risk of adverse immune-related events. We present a patient with widely metastatic melanoma who was initially treated with ipilimumab and subsequently with nivolumab. After four infusions of nivolumab, he developed subacute multifocal central nervous system (CNS) demyelination. Nivolumab was discontinued and, despite immunosuppressive therapy, the largest lesion progressed significantly, whereas another lesion showed radiographic improvement. After further progression, the patient succumbed to his CNS lesions 4 months later. Autopsy revealed extensive demyelination, a mild multifocal T-cell–rich perivascular lymphoid infiltrate, abundant macrophages, and necrosis. There was no metastatic melanoma in the brain. CNS demyelination has not been described in association with nivolumab. We hypothesize that the combination therapy of ipilimumab and subsequent nivolumab accounted for the severity of the demyelinating process in this patient. This case, with comprehensive clinical, molecular, and neuropathologic characterization, illustrates the need for awareness of these potential CNS complications with the use of multiple checkpoint inhibitors. Cancer Immunol Res; 3(12); 1299–302. ©2015 AACR.

Human Schwannomas Express Activated Platelet-Derived Growth Factor Receptors and c-kit and Are Growth Inhibited by Gleevec (Imatinib Mesylate)

Schwannomas, although benign, can be fatal or give rise to significant morbidity due to an unpredictable growth rate. They can reoccur after surgery or radiation, current treatments each with significant inherent risks. These risks are further amplified in neurofibromatosis type 2 (NF2), a germ line predisposition syndrome characterized by multiple schwannomas, underlying the need for biological targeted therapies. Gleevec (STI571, imatinib mesylate), in addition to the bcr-abl oncogene in chronic myelogenous leukemia, inhibits c-kit and platelet-derived growth factor receptor (PDGFR) signaling, thereby expanding its use to several malignant and benign human diseases. In the present study, we show that human sporadic and NF2-associated schwannomas have increased expression along with activation of PDGFR-alpha, PDGFR-beta, and c-kit receptors, compared with normal or traumatic nerve. Using the human NF2-null HEI-193 schwannoma cell line, Gleevec inhibited schwannoma viability, proliferation, and anchorage-independent growth, as well as induced apoptosis in a dose-dependent manner (IC(50) 5-10 micromol/L). These antitumorigenic effects were correlated to inhibition of PDGFR-alpha, PDGFR-beta, and c-kit activation/phosphorylation and major downstream signaling pathways. Lack of robust xenograft or transgenic models of schwannomas prevents extension of these studies in vivo. However, the established long track record and tolerable toxicity of Gleevec already in clinical use and our preclinical data lead us to propose that Gleevec should be evaluated in human schwannomas with shown progressive growth.

Histologically Confirmed Hippocampal Structural Features Revealed by 3T MR Imaging: Potential to Increase Diagnostic Specificity of Mesial Temporal Sclerosis

BACKGROUND AND PURPOSE: With appropriate selection, temporal lobe epilepsy is potentially curable with surgical intervention achieving seizure freedom in ∼80% of individuals. MR imaging−based identification of MTS remains central to the selection process but currently relies on qualitative visual analysis. We sought to determine if new ultrastructural hippocampal details seen on 3T MR imaging had histopathologic correlates and whether these could serve as a useful tool in MTS identification. MATERIALS AND METHODS: Patients undergoing selective anterior temporal lobectomy (n = 5) were scanned using 3T MR imaging preoperatively. En bloc resections were rescanned and subsequently prepared for histopathologic analysis of all hippocampal layers in the CA1–3 regions. Using a newly identified landmark from 3T FSTIR coronal images in 20 patients with histologically confirmed MTS, blinded studies compared ipsilateral and contralateral sides to generate threshold measurements for application in a fast quantitative analysis tool. RESULTS: Histopathologic analysis and correlation with 3T imaging of en bloc resections identified the low-intensity signal as the stratum lacunosum. MTS was associated with extensive gliosis throughout the CA1–3 regions, with loss of tissue thickness in the stratum pyramidale most pronounced in CA1. Fast quantitative analysis by using the stratum lacunosum as a landmark provided a test that identifies MTS with a SN of 70% and SP of 85%. CONCLUSIONS: Here we delineated ultrastructural hippocampal details seen on 3T MR imaging in both the in vivo and ex vivo setting, correlating these with histopathologic features consistent with MTS, and provided preliminary data suggesting their utility in the development of a quantitative analysis assessment tool for application in surgical-candidate selection.