Ultrastructural features of NUT midline carcinoma.

Midline carcinomas associated with the nuclear protein in testis (NUT) gene rearrangement are rare, aggressive tumors that have been diagnosed most commonly in the head, neck, mediastinum, and upper aerodigestive tract. The ultrastructural features associated with this tumor have thus far received only brief comment and have never been illustrated. The authors provide a more extensive description and illustrate the electron microscopic findings in a typical case of NUT midline carcinoma, confirmed by cytogenetic and fluorescence in situ hybridization studies. This tumor was composed of cells displaying large, irregularly shaped nuclei with prominent compact nucleoli and abundant cytoplasm containing prominent bundles of tonofilaments, occasional clusters of pleomorphic granules, small numbers of lipid inclusions, and rare glycogen deposits. The cells exhibited stubby microvillous projections, were intermittently enveloped by basal lamina, and were interjoined by numerous well-formed desmosomal-type junctions and occasional junctional complexes. The authors propose that this constellation of ultrastructural features can prove helpful in discriminating NUT midline carcinoma from similar appearing entities.

Papillary tumor of the pineal region: ultrastructural study of a case.

Papillary tumor of the pineal region (PTPR) is a recently classified neuroepithelial tumor for which there has been little comprehensive ultrastructural study. Here, we describe the radiographic, intraoperative, histologic, immunohistochemical, and in-depth ultrastructural findings in a case of PTPR. This study corroborates that PTPR has concomitant ependymal, neuroendocrine, and secretory features, and details novel ultrastructural as well as immunohistochemical features that further this argument. Discrepancies with prior descriptions of PTPR are described, as these differences may reflect phenotypic variability in this rare tumor, and the ultrastructural features that relate to the putative ependymal origin of the entity are emphasized.

Plexiform fibrohistiocytic tumor: ultrastructural studies may aid in discrimination from cellular neurothekeoma.

Plexiform fibrohistiocytic tumor is a low-grade soft tissue malignancy that can at times be difficult to differentiate from the less biologically aggressive cellular neurothekeoma. The two entities, which may display identical clinical and histological features, cannot be distinguished by immunohistochemical or molecular diagnostic means. Electron microscopy may enable the accurate identification of problematic examples and thus aid in resolving these occasionally occurring diagnostic dilemmas. To illustrate typical variations in the ultrastructural appearance of plexiform fibrohistiocytic tumor, the authors present two diagnostically noncontroversial examples, and to demonstrate the potential diagnostic utility of electron microscopy in this setting, they present an example of plexiform fibrohistiocytic tumor that could not otherwise have been distinguished from cellular neurothekeoma.

Infantile cardiomyopathy caused by the T14709C mutation in the mitochondrial tRNA glutamic acid gene.

A 6-week-old child presented with hypotonia, myopathy, and a rapidly worsening dilated cardiomyopathy with severe atrial and ventricular arrhythmias and pulmonary hypertension, which proved fatal at age 3 months. Biochemical analysis showed a combined deficiency of the enzymatic activities of complexes I and IV and molecular studies identified a T14709C mutation in the mitochondrial tRNA glutamic acid gene. A review of symptomatology in patients with this mutation shows that it mainly presents in childhood or young adults with mild myopathy and diabetes mellitus. Infants with a high, nearly homoplasmic mutant load can present with more severe symptoms including cardiomyopathy. Families with this mitochondrial DNA mutation should be aware that increased mutant load in a subsequent generation may result in severe and often fatal cardiac symptoms.

Renal medullary carcinoma: ultrastructural studies may benefit diagnosis.

Renal medullary carcinoma is a recently described highly aggressive malignancy that in most instances exhibits a constellation of clinical and light microscopic features sufficiently distinctive to enable a quick and confident diagnosis. Presented are three examples where, because of unusual elements in the clinical presentation, electron microscopic examination proved beneficial in establishing the diagnosis.

Perivascular elastic fibers: a diagnostic feature of ependymoma.

To assess the diagnostic potential of perivascular elastic fiber detection as an indicator of ependymoma, the authors performed ultrastructural studies on a large series of pediatric brain tumors. Elastic fibers were demonstrated by electron microscopy in 38 of 50 (76%) ependymomas, 2 of 25 (8%) choroid plexus tumors, 0 of 100 (0%) medulloblastomas, and 0 of 100 (0%) astrocytomas. In some poorly differentiated examples, elastic fibers were initially the sole indicator of ependymal differentiation. The authors conclude that the sensitivity and specificity of this feature is sufficient to render demonstration of perivascular elastic fibers a useful diagnostic indicator of ependymoma.

Primary intracranial Ewing's sarcoma with unusual features.

Pediatric primary "small round blue cell" tumors in the CNS represent several entities, some more common than others. Ewing sarcoma/peripheral primitive neuroectodermal tumor (ES/pPNET) is rare and must be distinguished from other tumors such as medulloblastoma [1, 2], atypical rhabdoid/teratoid tumor, ependymomal tumors, metastatic sarcomas, hematologic malignancies, and other mimics. Although therapy for ES/pPNET is effective, it brings severe side effects, including cardiac toxicity, making correct recognition important [3]. As small blue cell tumors look similar, diagnosis often depends on special stains, immunohistochemistry, and molecular techniques. While the combination of membranous immunohistochemical reactivity for CD99 with cytoplasmic glycogen provides effective screening, demonstration of characteristic translocations of EWSR1 (chromosome 22) or FUS (chromosome 16) by fluorescent in situ hybridization (FISH) can confirm the diagnosis. We are reporting three primary ES/pPNET of the CNS, two of which occurred in children. While the adult case demonstrates the classic histopathology, the two pediatric cases have histopathology that significantly deviates from the usual. One is suggestive of a primary sarcoma, and the other mimics an ependymoma, but all three cases are confirmed with FISH. These observations suggest that primary ES in the CNS may have histology different from the classic morphology and a high index of suspicion should be maintained in order to make the correct diagnosis. A search of the literature suggests that these tumors are most frequently seen in children and young adults. Imaging often shows a supratentorial enhancing mass that touches the leptomeninges. Survival over three years is good but long term prognosis is unknown [3, 4].

Ciliary inclusion disease: report of a new primary ciliary dyskinesia variant.

Biopsies from 6 children with clinical presentations suggestive of primary ciliary dyskinesia (PCD) displayed respiratory epithelial cells with disorganized accumulations of basal bodies within the cytoplasm and large intracytoplasmic vesicles into which projected numerous microvilli and cilia. Microvilli, but few cilia, were present at the cell surface. Ultrastructural study revealed a variety of nonspecific abnormalities but demonstrated the cilia generally to be morphologically normal, suggesting that the cause of cilia malfunction was not any recognized primary cause or secondary effect. Repeat studies from 2 patients produced similar findings. It is proposed that this entity, termed ciliary inclusion disease, represents a variant form of PCD manifesting as a consequence of improper ciliogenesis caused by inhibited cytoskeleton-regulated migration of basal bodies to the luminal surface of the airway respiratory epithelial cells.

Features of intraventricular tanycytic ependymoma: report of a case and review of literature.

Tanycytic ependymoma is the rarest variant of ependymoma and occurs primarily in the spinal cord. Intracranial cases are even rarer. Only 9 ventricular and 5 subcortical tanycytic ependymoma have been reported in the literature. Amongst the 9 ventricular cases, only one tumor arose from the third ventricle. We report here another case of tanycytic ependymoma arising from the third ventricle completed with immunohistochemical, ultrastructural, and molecular pathology study. The patient was a 44 year-old male who presented with headache, nausea and visual disturbances of a few months duration. Neuroradiological findings showed a well-defined mass arising from the posterolateral wall of third ventricle. Histologically the tumor was composed of monotonous spindle cells arranged in fascicles without definitive perivascular rosettes. The tumor cells were diffusely positive for glial fibrillary acidic protein and epithelial membrane antigen, showed faint immunoreactivity for synaptophysin but were negative for neurofilament proteins and Ki-67 was less than 1%. Molecular studies showed absence of isocitrate dehydrogenase gene 1 and 2 mutation. A diagnosis of tanycytic ependymoma (TE) was made. From literature review with our current case included, intraventricular tanycytic ependymomas ranged from 1.8 to 4.0 cm. The age of patients ranged from 3.5 to 75 years with a mean age of 37.5 and a male predominance. The tumors occurred as well-defined, solitary ventricular mass without significant peritumoral edema with or without cystic changes. Histopathology and immunohistochemical profile are rather similar among different tumors. The immediate to short term outcome is excellent but long term follow up data is lacking.

Three linked vasculopathic processes characterize Kawasaki disease: a light and transmission electron microscopic study.

BACKGROUND: Kawasaki disease is recognized as the most common cause of acquired heart disease in children in the developed world. Clinical, epidemiologic, and pathologic evidence supports an infectious agent, likely entering through the lung. Pathologic studies proposing an acute coronary arteritis followed by healing fail to account for the complex vasculopathy and clinical course. METHODOLOGY/PRINCIPAL FINDINGS: Specimens from 32 autopsies, 8 cardiac transplants, and an excised coronary aneurysm were studied by light (n=41) and transmission electron microscopy (n=7). Three characteristic vasculopathic processes were identified in coronary (CA) and non-coronary arteries: acute self-limited necrotizing arteritis (NA), subacute/chronic (SA/C) vasculitis, and luminal myofibroblastic proliferation (LMP). NA is a synchronous neutrophilic process of the endothelium, beginning and ending within the first two weeks of fever onset, and progressively destroying the wall into the adventitia causing saccular aneurysms, which can thrombose or rupture. SA/C vasculitis is an asynchronous process that can commence within the first two weeks onward, starting in the adventitia/perivascular tissue and variably inflaming/damaging the wall during progression to the lumen. Besides fusiform and saccular aneurysms that can thrombose, SA/C vasculitis likely causes the transition of medial and adventitial smooth muscle cells (SMC) into classic myofibroblasts, which combined with their matrix products and inflammation create progressive stenosing luminal lesions (SA/C-LMP). Remote LMP apparently results from circulating factors. Veins, pulmonary arteries, and aorta can develop subclinical SA/C vasculitis and SA/C-LMP, but not NA. The earliest death (day 10) had both CA SA/C vasculitis and SA/C-LMP, and an "eosinophilic-type" myocarditis. CONCLUSIONS/SIGNIFICANCE: NA is the only self-limiting process of the three, is responsible for the earliest morbidity/mortality, and is consistent with acute viral infection. SA/C vasculitis can begin as early as NA, but can occur/persist for months to years; LMP causes progressive arterial stenosis and thrombosis and is composed of unique SMC-derived pathologic myofibroblasts.

Platelet-activating factor-mediated endosome formation causes membrane translocation of p67phox and p40phox that requires recruitment and activation of p38 MAPK, Rab5a, and phosphatidylinositol 3-kinase in human neutrophils.

Neutrophils (polymorphonuclear leukocytes, PMNs) are vital to innate immunity and receive proinflammatory signals that activate G protein-coupled receptors (GPCRs). Because GPCRs transduce signals through clathrin-mediated endocytosis (CME), we hypothesized that platelet-activating factor (PAF), an effective chemoattractant that primes the PMN oxidase, would signal through CME, specifically via dynamin-2 activation and endosomal formation resulting in membrane translocation of cytosolic phagocyte oxidase (phox) proteins. PMNs were incubated with buffer or 2 muM PAF for 1-3 min, and in some cases activated with PMA, and O(2)(-) was measured, whole-cell lysates and subcellular fractions were prepared, or the PMNs were fixed onto slides for digital or electron microscopy. PAF caused activation of dynamin-2, resulting in endosomal formation that required PI3K and contained early endosomal Ag-1 (EEA-1) and Rab5a. The apoptosis signal-regulating kinase-1/MAPK kinase-3/p38 MAPK signalosome assembled on Rab5a and phosphorylated EEA-1 and Rab GDP dissociation inhibitor, with the latter causing Rab5a activation. Electron microscopy demonstrated that PAF caused two distinct sites for activation of p38 MAPK. EEA-1 provided a scaffold for recruitment of the p40(phox)-p67(phox) complex and PI3K-dependent Akt1 phosphorylation of these two phox proteins. PAF induced membrane translocation of p40(phox)-p67(phox) localizing to gp91(phox), which was PI3K-, but not p47(phox)-, dependent. In conclusion, PAF transduces signals through CME, and such GPCR signaling may allow for pharmacological manipulation of these cells to decrease PMN-mediated acute organ injury.

Ependymomas with neuronal differentiation: a morphologic and immunohistochemical spectrum.

The category of mixed glioneuronal tumors of the CNS is rapidly losing its definition as encompassing tumors composed of histologically distinct neuron variants and glia. We encountered five ependymomas with neuronal differentiation seen in two by histology, in two by immunohistochemistry alone, and in one by electron microscopy. Antibodies against GFAP, S-100 protein, neurofilament protein, chromogranin, synaptophysin, Neu-N, and EMA were applied. Ultrastructural studies were also performed. In addition, 33 randomly selected ependymomas of various histologic types were screened for these same antigens. Cases 1 and 2 were anaplastic and showed clearly defined neuropil islands or pale islands as in nodular desmoplastic medulloblastoma, respectively. The tumors affected a 16-year-old male and a 5-year-old female and involved the right frontoparietal lobe and fourth ventricle, respectively. The islands were positive for synaptophysin and Neu-N (cases 1 and 2), and chromogranin (case 1). Cases 3-5, as well as 7 of the 33 screened ependymomas, showed a suggestion of neuronal differentiation by immunohistochemistry alone, including immunoreactivity for Neu-N (n = 8), synaptophysin (n = 4), neurofilament protein (n = 4), and chromogranin (n = 2). Five tumors each were WHO grade II and III. Electron microscopy performed on the two cases with neuronal islands demonstrated microtubule bundles and dense core granules (case 1) and poorly differentiated cells with high nuclear/cytoplasmic ratios, with intermediate filament accumulation and rare cilia (case 2). Cases identified by immunohistochemistry or electron microscopy demonstrated dense core granules (n = 5) and aligned microtubules (n = 3). Neuronal differentiation occurs in ependymomas but is less frequently definitive (histologic, ultrastructural) than merely a limited immunohistochemical finding. The clinical significance of these observations is unknown but deserves further exploration.

The spectrum of pediatric tumors in infancy, childhood, and adolescence: a comprehensive review with emphasis on special techniques in diagnosis.

The spectrum of pediatric tumors varies considerably, from those derived from blastemal cells in various organ systems to proliferations of soft tissue supporting cells to hamartomatous processes that mimic malignant tumors. Small round cell tumors are often undifferentiated or poorly differentiated, making it difficult sometimes to provide a definitive diagnosis. Both benign and malignant tumors require a coordinated method for diagnosis, and need a comprehensive evaluation to provide the most appropriate diagnosis for designing therapy and predicting prognosis. Pediatric tumors require the integration of routine histopathologic examination with histochemical, immunocytochemical, ultrastructural, cytogenetic, and diagnostic molecular pathology techniques. This review provides updated guidelines with respect to the application of these special techniques in this rapidly evolving diagnostic arena.

Benign müllerian papilloma of childhood.

Benign müllerian papilloma of the female reproductive tract is a rare childhood tumor that can easily be mistaken by those unfamiliar with the entity for botryoid rhabdomyosarcoma. Ultrastructural findings have been mentioned only in two individual case reports, and these both were issued many years ago. The aim of this update is to familiarize the reader with the clinical, light, and electron microscopic features associated with this distinctive entity, and thereby hopefully preclude the risk of making a serious diagnostic error. Two cases are illustrated, one very typical in its presentation and the other less so.

Ultrastructural spectrum of medulloblastoma with immunocytochemical correlations.

Electron microscopy was used to examine 72 cases of medulloblastoma to better characterize the ultrastructural spectrum of this tumor. Twenty-four cases showed prominent neural differentiation. Twenty-three cases showed minimal (21) or no (2) recognizable neural differentiation, and the remainder of the cases (25) showed intermediate differentiation. All 42 cases tested stained for neuron-specific enolase, 28 for synaptophysin, and 12 for neurofilament protein. All cases showed strong reactivity for glial fibrillary acidic protein (GFAP) within reactive astrocytes. Three cases showed reactivity for GFAP within tumor cells. Medulloblastoma exhibits a broad spectrum of neural differentiation, with nearly all cases showing at least some degree of this change, and it universally exhibits participation of reactive astrocytes which can create a potential for diagnostic confusion.

Intranuclear rod myopathy, a rare and morphologically striking variant of nemaline rod myopathy.

A 4-year-old boy with muscle weakness underwent skeletal muscle biopsies. Light microscopy showed distinct eosinophilic inclusions within the majority of muscle cell nuclei, but none in the cytoplasm. Electron microscopy revealed crystalline, round to rod-shaped inclusions in the muscle cell nuclei. The inclusions stained positively for alpha-actinin. Intranuclear inclusions identical to those seen here have been described in rare cases of nemaline rod myopathy, though almost always together with classic intracytoplasmic rods. This case illustrates the importance of electron microscopy in the diagnosis of rare myopathies and in the characterization of cellular inclusions of unknown origin.

Microvillous inclusion disease with abundant vermiform, electron-lucent vesicles.

A 3-month-old girl with congenital secretory diarrhea underwent a duodenal biopsy. Histologic study showed villous atrophy and large amounts of PAS-positive material within enterocyte cytoplasm. Despite a clinical suspicion of microvillous inclusion disease, 2 sessions of electron microscopy were unsuccessful in detecting the diagnostic inclusions. Instead, large aggregates of electron-lucent, vermiform membranous vesicles were observed in enterocyte cytoplasm, corresponding to the PAS-positive material. A third attempt at electron microscopy was successful in detecting small numbers of microvillous inclusions. These and other recently reported cases document an expanding spectrum of ultrastructural findings in this disease, including examples where the classic microvillous inclusions are overshadowed by other features.

Sclerosing hemangioma of the lung in a young woman with cutaneous melanoma: the role of electron microscopy in preventing an erroneous diagnosis of metastasis.

A young woman with a melanoma of the left forearm was found to have a right lung mass. This was initially interpreted as metastatic melanoma on the basis of clinical, radiographic, and light microscopic features, together with positive staining of tumor cells with antibody HMB-45. Electron microscopic examination performed for confirmation of the diagnosis revealed no evidence of melanocytic differentiation. Instead, there were features suggestive of the alternative diagnosis of sclerosing hemangioma (SH). This diagnosis was confirmed with additional immunocytochemical stains. To the authors' knowledge this is the first report of HMB-45 positivity in SH. This case illustrates a potentially disastrous diagnostic pitfall in interpreting lung tumors in patients with melanoma, and the vital role of electron microscopy in resolving conflicting and/or misleading immunocytochemical results.

Biliary diversion for progressive familial intrahepatic cholestasis: improved liver morphology and bile acid profile.

BACKGROUND AND AIMS: Progressive familial intrahepatic cholestasis (PFIC) is characterized by pruritus, intrahepatic cholestasis, low serum gamma-glutamyltransferase levels, and characteristic "Byler bile" on electron microscopy. Many patients require liver transplantation, but partial external biliary diversion (PEBD) has shown therapeutic promise. However, the effect of PEBD on liver morphology and bile composition has not been evaluated. METHODS: We reviewed liver biopsy specimens from 3 children with low gamma-glutamyltransferase PFIC before and after PEBD. Follow-up liver biopsies were performed 9-60 months after PEBD. Light and electron microscopic features were scored blindly. Biliary bile acid composition was analyzed by gas chromatography-mass spectrometry before and after PEBD in 1 patient and after PEBD in 2 patients. RESULTS: Following PEBD, all patients improved clinically. Preoperative biopsy specimens showed characteristic features of PFIC, including portal fibrosis, chronic inflammation, cholestasis, giant cell transformation, and central venous mural sclerosis. Ultrastructural findings included coarse, granular canalicular Byler bile, effaced canalicular microvilli, and proliferative pericanalicular microfilaments. Following diversion, histology showed almost complete resolution of cholestasis, portal fibrosis, and inflammation with resolution of ultrastructural abnormalities. Biliary bile acids before PEBD consisted predominantly of cholic acid. After PEBD, the proportion of chenodeoxycholic acid increased significantly in 1 patient and was above the PFIC range in a second patient. CONCLUSIONS: The resolution of hepatic morphologic abnormalities following PEBD supports PEBD as an effective therapy for PFIC. The improved biliary bile acid composition suggests enhanced bile acid secretion after PEBD, perhaps by induction of alternative canalicular transport proteins.

Molecular genetic analysis of a small bowel primitive neuroectodermal tumor.

We present a pediatric peripheral primitive neuroectodermal tumor (pPNET) localized exclusively to the small bowel. The tumor presented in an adolescent male and the diagnosis was confirmed by electron microscopy, CD99 immunopositivity, and molecular genetic analysis that demonstrated an EWS-FLI1 type 2 fusion transcript. This case report and a review of the literature underscore the considerable phenotypic overlap in EWS-related tumors in this site and the necessity for molecular genetic analysis to permit accurate classification.