Hypertension after neonatal uninephrectomy in rats precedes glomerular damage.

The present study was designed to determine whether adult hypertension caused by a reduced number of nephrons from birth is due to preceding glomerular damage. Newborn male Sprague-Dawley rat pups were uninephrectomized during the first 24 hours after birth (UNX rats). At 20 weeks of age, chronically instrumented UNX animals were hypertensive on a normal-sodium (0.20%) diet compared with sham-operated controls (142+/-2 versus 124+/-2 mm Hg in controls). Body weights and the total kidney-to-body weight ratio were not significantly different in adult UNX animals compared with controls. Glomerular filtration rate (GFR) was reduced by 49% in UNX rats (1.85+/-0.24 versus 3.65+/-0.22 mL/min). Urine protein excretions were higher in UNX rats (20+/-2 versus 7+/-1 mg/d in controls). On a high-sodium (3.15%) diet, arterial pressure increased more in UNX than in controls (28+/-9 versus 3+/-1 mm Hg). In contrast, in animals studied at 8 weeks of age, GFR was only reduced by 26% in UNX animals (2.02+/-0.06 versus 2.73+/-0.07 mL/min). Their hypertension (125+/-2 versus 117+/-2 mm Hg) was also salt sensitive (increase on high-sodium diet of 35+/-11 versus 8+/-2 mm Hg in controls) but was not associated with proteinuria or histological signs of glomerular disease. Number of glomeruli per kidney in UNX animals was not different from controls, but individual glomerular volume increased by 41%. Thus, surgical removal of 50% of the nephrons, when done during development, causes reduced renal function and salt-sensitive hypertension in adulthood. Hypertension is present earlier in life than signs of glomerular disease, which suggests that hypertension is a major contributor to rather than primarily resulting from onset of renal disease.

Role of electron microscopy and other special techniques in the diagnosis of childhood round cell tumors.

A series of case presentations show unique challenges associated with childhood round cell tumors and the role of ancillary techniques in diagnosis. Electron microscopy is shown to be the most powerful individual technique. Immunohistochemistry is less effective but also essential. Other ancillary techniques may provide needed additional diagnostic information. Because this is an area where it is of great importance to secure the most rapid, accurate, and specific diagnosis possible, an integrated multimodal approach is recommended--incorporating light microscopic, electron microscopic, and immunohistochemical studies as a matter of routine, and providing for cytogenetic and/or molecular diagnostic studies as indicated.

Use of electron microscopy and other special techniques in the investigation of suspected specimen contamination.

Contamination of a biopsy or surgical specimen with spurious tissue is an uncommon but potentially disastrous event. In this regard, the case of a 5-year-old boy referred for treatment of an abdominal tumor is presented. Sections made from paraffin blocks brought by the family showed both neuroblastoma and a spindle cell sarcoma, initially suggesting the possibility of divergent or mixed differentiation. However, the resemblance of the spindle cell component to well-differentiated leiomyosarcoma rather than rhabdomyosarcoma raised the suspicion that a specimen contamination had occurred. Electron microscopy was instrumental in confirming the smooth muscle nature of the sarcomatous component, leading to a fluorescence in situ hybridization study, which established that this component was incompatible with the patient's gender. This case illustrates that even when the light microscopic differential has been compromised by specimen mishandling, electron microscopy can at times provide useful information regarding specimen identity, as well as assist in sorting out the correct diagnosis.

Role of electron microscopy in the diagnosis of metabolic storage diseases affecting the nervous system of children.

Metabolic storage diseases are among the most challenging diagnostic problems faced by clinicians and pathologists. There is considerable variation in the diagnostic approach to these diseases between different institutions and between different diagnosticians. Much of this variation arises from differences in the availability of and physician confidence in the diagnostic modalities employed to characterize these disorders. Recent advances in the biochemistry and molecular genetics of these diseases have produced some skepticism about the continued relevance of traditional morphologic techniques, including electron microscopy, in their diagnosis. It is the opinion of the authors that this concern is premature and that electron microscopy continues to play a vital role, particularly in the diagnosis of those entities that challenge the classic definitions of lysosomal storage diseases. The authors present a series of cases illustrating different situations where electron microscopy can provide timely, cost-effective, and accurate information in the workup of such diseases.

Primary leiomyosarcoma of brain in an adolescent with common variable immunodeficiency syndrome.

A 14-year-old girl with common variable immunodeficiency syndrome was found to have a low-grade malignant neoplasm arising in the left temporal lobe of the brain. Ultrastructural and immunohistochemical studies established a diagnosis of leiomyosarcoma, despite the rarity of this tumor in children. In situ hybridization with the EBER probe revealed essentially all of the neoplastic cells to be infected with Epstein-Barr virus (EBV). Children with the acquired immunodeficiency syndrome (AIDS) are known to exhibit an increased incidence of smooth muscle tumors associated with EBV. Similar tumors have been reported in EBV-infected patients undergoing therapeutic immunosuppression. This appears to be the first reported case of childhood leiomyosarcoma where the cause of the underlying immunodeficiency was a genetic rather than acquired disorder. The authors conclude that electron microscopy, immunohistochemistry, and other ancillary techniques are essential in the evaluation of unusual tumors in immunocompromised children, whether the cause is hereditary or acquired.

Appraisal of the comparative utility of immunohistochemistry and electron microscopy in the diagnosis of childhood round cell tumors.

To provide an objective assessment of the comparative utility of fluorescence- and peroxidase-based immunohistochemistry and electron microscopy, an observer blinded study was conducted under realistic study conditions utilizing a large sampling of poorly differentiated pediatric round cell tumors. Working independently, using a single ancillary technique of particular expertise, each of three investigators attempted to render a specific diagnosis with regard to 50 diagnostically challenging tumors. The results were compared against the subsequent "file diagnosis" established by consensus with all relevant information made available. A grading scheme was applied wherein points were awarded based on the accuracy and confidence of diagnosis. A comparative efficiency rating, expressed as a percentage, was formulated by dividing the number of points awarded each technique by the total number of points theoretically available. Electron microscopy proved superior overall, with an efficiency rating of 89%. Immunoperoxidase and immunofluorescence studies yielded efficiency ratings of 71 and 61%, respectively. Used in combination, the techniques achieved an efficiency rating of 95%. Application of these ancillary techniques resulted in a revision of the provisional diagnosis in 11 of 50 cases, and left only two cases without a firm specific diagnosis.

Ultrastructure of cellular congenital mesoblastic nephroma.

A detailed ultrastructural description of the cellular variant of congenital mesoblastic nephroma (CMN) is presented and compared to the classical form. Studied were 9 cases of the cellular variant, 6 mixed (cellular/classical) tumors, and 1 classical CMN. The occurrence of a broad selection of ultrastructural features was assessed using a semiquantitative scoring system. The results indicate that cellular CMNs are composed mainly of primitive mesenchymal cells, but also usually contain varying numbers of differentiating fibroblasts and myofibroblasts. This entity thus bears a closer resemblance at the ultrastructural level of organization to infantile fibrosarcoma than to conventional fibrosarcoma. Electron microscopy can be useful in distinguishing this relatively benign entity from the several malignancies with which it is sometimes confused.

Focal versus diffuse anaplasia in Wilms tumor--new definitions with prognostic significance: a report from the National Wilms Tumor Study Group.

Anaplasia, defined by the presence of extreme nuclear and mitotic atypia, is a potent marker of adverse prognosis in Wilms tumor (WT). Anaplastic WT cells apparently have increased resistance to therapy rather than increased aggressiveness. The distribution of anaplasia should therefore have critical prognostic relevance. The original definitions for focal anaplasia (FA) and diffuse anaplasia (DA) were based on quantitative rather than topographical criteria and lacked prognostic significance. A new definition was developed based on the distribution of anaplastic changes within the tumor: FA applies only to tumors with anaplasia confined to one or a few discrete loci within the primary tumor, with no anaplasia or marked nuclear atypia elsewhere. This revised definition was evaluated in 165 cases with anaplastic WT entered on the third and fourth National Wilms Tumor Study. Only three relapses and one death occurred among 39 cases with FA, regardless of tumor stage, a result comparable to that for nonanaplastic WT. Eight children with metastases at diagnosis and FA in the primary tumor were alive and free of relapse; 22 of 23 children with stage IV DA WT died of tumor. This new definition reinforces the importance of carefully documenting the exact site from which each tumor section is obtained.

Solenoid pumps for flow injection analysis.

Methods employing flow injection analysis (FIA), particularly for in situ seawater techniques, would benefit from reduction in pump size and power requirement, longer maintenance intervals, and the ability to incorporate microprocessor control of each reagent and sample flow stream. In this work, the peristaltic pump of a conventional FIA system was replaced by three solenoid-driven diaphragm pumps with integral Viton check valves, and the system was tested by performing the simple nitrite analysis, which has well-defined FIA performance characteristics. Sixty injections per hour were possible with flow rates of 0.5 mL/min for reagents and sample. The coefficient of variation was 1% for 10 µM NO(2)(-) concentrations, and the detection limit was less than 0.1 µM NO(2)(-). These values match the reported performance for this method using peristaltic pumps.

Intraoperative radiotherapy in the treatment of neuroblastoma: report of a pilot study.

BACKGROUND: External beam radiotherapy in advanced neuroblastoma is limited by the volume of normal radiosensitive tissues included in the radiation field. Limitations to external radiation are the late effects to these tissues. Intraoperative radiotherapy (IORT) delivers a single high-radiation dose to a tumor while displacing normal tissues that would have been included in an external field. Standard external radiotherapy can still be done after "boost" IORT. METHODS: Eight advanced-stage neuroblastoma patients who received IORT as part of their multimodality therapy were reviewed to identify the impact of IORT on operative time, complications, and tumor control in the treatment field. The IORT was accomplished by patient transport from the OR to the radiation therapy suite; these were separated by three floors. RESULTS: IORT added 30-75 min to the operative procedure. Tumors in the resection/IORT fields showed no evidence of disease (one), stable tumor size (six), and tumor recurrence (one). Two complications were identified: a urinary fistula and CO2 retention, which was detected and corrected before the IORT. Neither of these complications was related to the IORT. Two patients who had subsequent tumor resection after IORT demonstrated tumor differentiation to ganglioneuromatous tissue. CONCLUSIONS: IORT usually can be completed in less than an hour. No IORT-associated complications were identified. IORT along with maximal tumor resection, external radiation, and chemotherapy enhances local tumor control.

The clinicopathologic spectrum of putative extrarenal rhabdoid tumors. An analysis of 42 cases studied with immunohistochemistry or electron microscopy.

The existence of extrarenal rhabdoid tumor (ERRT) as a discrete pathologic entity has been controversial despite frequent reports of its occurrence. We performed immunohistochemistry, electron microscopy, or both on 42 cases with this diagnosis sent in consultation to us. Only 12 of the 42 neoplasms had the histological findings of "classic" malignant rhabdoid tumor of the kidney; the remainder displayed a variety of neural, epithelial, myoid, mesenchymal, or ependymal patterns. Electron microscopy also showed that most possessed neural, epithelial, or ependymal features. Immunohistochemistry generally revealed marked polyphenotypia, with immunoreactivity to a wide array of antibodies against neural, epithelial, glial, and myogenic markers. A specific tissue-based diagnostic category could not be assigned in only 11 of the 42 cases, seven of which lacked material for a comprehensive ultrastructural or immunohistochemical study. We conclude that tumors currently diagnosed as ERRT represent a heterogeneous group of neoplasms that may form unique subsets of known entities within the specific site where they arise or that may defy classification into a specific alternative category. Our findings lead us to believe that the term ERRT is not valid as representing a specific diagnostic entity and to prefer the term "poorly differentiated neoplasm with rhabdoid features" for undifferentiated tumors.

The relationship between microsubstaging variables, age at diagnosis, and tumor weight of children with stage I/favorable histology Wilms' tumor. A report from the National Wilms' Tumor study.

BACKGROUND: The purpose of this study was to determine the relationship between histologic microsubstaging variables, patient age, and tumor specimen weight in patients with Stage I/favorable histology Wilms' tumors. METHODS: The authors reviewed all randomized patients from the Fourth National Wilms' Tumor Study, who had Stage I/favorable histology Wilms' tumors evaluated for one or more of the microsubstaging variables: (1) the presence of an inflammatory pseudocapsule, (2) renal sinus invasion, (3) tumor in the intrarenal vessels, and (4) tumor capsule invasion. The authors determined the correlation between microsubstaging variables and age at diagnosis or tumor specimen weight. RESULTS: Patients who were younger than 2 years of age at diagnosis were significantly more likely to have all negative microsubstaging variables. Patients who had tumors weighing less than 550 g were more likely to have all negative microsubstaging variables. However, neither renal sinus invasion nor tumor in the intrarenal vessels was more frequent in tumors weighing more than 550 g. CONCLUSIONS: An age at diagnosis of younger than 2 years and a tumor specimen weight of less than 550 g are highly correlated with the absence of adverse microsubstaging variables. The clinical variables of age at diagnosis and tumor specimen weight, compared with the assessment of microsubstaging variables, have the practical advantage of being more objectively determined and not requiring a central pathologic review for confirmation.

Extrarenal angiomyolipoma with melanocytic and hibernoma-like features.

Angiomyolipoma is a tumor commonly occurring in the kidney, but occasionally found in extrarenal sites. Retroperitoneal angiomyolipoma with unusual features presenting in a 39 year old woman with hypertension is reported in this paper. Tumor fat was inconspicuous, and present largely as hibernoma-like microvesicular lipid. Tumor cells also demonstrated positivity for HMB-45 and S-100 protein, and by electron microscopy showed occasional cytoplasmic striated granules indistinguishable from stage II premelanosomes. However, electron microscopy and immunocytochemistry also confirmed the presence of a substantial myogenous component in the tumor, establishing the diagnosis of angiomyolipoma. The implications of these findings, and the role of immunocytochemistry and electron microscopy in the diagnosis of this tumor are discussed.

Primitive cerebral tumor with rhabdoid features: a case of phenotypic rhabdoid tumor of the central nervous system.

The rhabdoid tumor (RT) was first described as an aggressive neoplasm of unknown histogenesis affecting the kidneys of infants and young children, but has since been reported in all ages and in many other primary sites, including the central nervous system. It has been shown, however, that the histologic and cytologic features of RT can be mimicked by many other tumors of known histogenesis. For this and other reasons it remains controversial whether cases of putative extrarenal RT represent the same histogenetic entity as RT of the kidney (RTK), another entity or entities, or merely a diverse collection of unrelated tumors sharing a common morphologic phenotype. The present paper describes a lethal primary cerebral tumor in a 26-month-old Hispanic boy that was composed predominantly of cells exhibiting the "classic" rhabdoid phenotype by light microscopy. Immunocytochemical and ultrastructural studies disclosed features of primitive neuroglial differentiation not seen in RTK. The findings in this case, as well as evidence from other studies, would seem to support the notion that primary RT of the brain may in fact constitute a morphologic and clinicopathologic entity. However, that entity likely represents a distinctive type of neuroglial neoplasm, more closely related to other primitive brain tumors than to RTK.

Meningioma with chordoid features.

Meningioma is a relatively common intracranial tumor, occurring most frequently in adults, and is capable of a wide variety of growth patterns. We describe a meningioma in a child that had a peculiar chordomalike appearance. The pathologic findings and distinction from chordoma are discussed.

Ependymoma with signet-ring cells.

Two patients presented with unusual primary brain tumors having abundant signet-ring cells, for which electron microscopic study was necessary to establish the diagnosis of ependymoma. The light and electron microscopic features of these tumors are discussed, with brief comments on the differential diagnosis.