SEM Study of Apical Morphological Alterations in Primary Teeth with Vital and Necrotic Pulps

This study evaluated, by SEM, the morphology of human primary teeth roots. Twenty-four teeth were divided into 3 groups: pulp vitality (group I) and pulp necrosis without (group II) and with apical periodontitis (group III). Roots were analyzed by the presence of periodontal ligament (PDL) fibers and resorption areas. In groups I and II, presence of PDL fibers and absence of resorption were observed in all cases (100%), while all specimens (100%) of group III showed no PDL fibers and resorption areas. In conclusion, there are morphological differences in the apical region of primary teeth with different pulpal and periapical pathologies.     

Role of Immunofluorescence and Electron Microscopy in the Evaluation of Renal Biopsies in Nephrotic Syndrome in a Developing Country

ABSTRACT

To determine the role of immunofluorescence (IF) and electron microscopy (EM) in the evaluation of renal biopsies in a developing country, the authors carried out a study in 200 patients with nephrotic syndrome. Renal biopsies were studied by light microscopy, IF, and EM. IF study was useful in all, being essential in 23.5% and helpful in remaining cases. EM was useful in 94.5% cases, being essential in 43% and helpful in 51.5% cases. The results demonstrate that IF and EM are essential in the evaluation of renal biopsies in nephrotic syndrome and these should be employed in the pathologic evaluation of renal biopsies.     

Application of Pop-off Method to Bone Marrow and Peripheral Blood Specimens for Purposes of Electron Microscopy

In this paper, we describe a pop-off method applicable to the hematological field. Bone marrow or peripheral blood specimens from patients were placed on a clean glass slide and fixed immediately in 2% glutaraldehyde solution for 10 minutes. For the DAB reaction, the slide was immersed in the DAB reagent for 30 minutes, and post fixed with 1 % OsO₄ solution for 1 hour. Specimens on the slide were washed with buffer solution, dehydrated and polymerized directly on the slide. A gelatin capsule filled with Epon mixed monomer was then reversed over the specimen. After polymerization was completed, the specimen was popped off from the slide to the capsule and trimmed carefully to prepare for ultrathin sectioning. This method allows the entire sequence of tissue preparation to be carried out on the slide, from fixation to embedding, and even, especially in scanty specimens, including the DAB reaction. Electron microscopic findings in specimens prepared by this technique show excellent preservation and the absence of specific artifacts.     

Phenotype/Genotype Correlations in the Ultrastructure of Monogenetic Glomerular Diseases

Electron microscopy defined classic patterns of hereditary glomerular disease long before genetics revealed an underlying specific mutation. Genetic analysis is now easier to perform in clinical practice but an earlier optimism that genetics would predict disease severity and phenotype is challenged. The classic paradigm is Alport nephritis in which only a subset of mutations may predict glomerular abnormalities and disease severity. Interpretation of ultrastructural pathology of monogenetic diseases like Alport nephritis is complicated when the proband is the first family member to be diagnosed or there is discrepancy between clinical presentation and ultrastructural changes. In this review the authors have selected a dozen cases representative of common monogenetic glomerular diseases as a platform to discuss the utility of diagnostic electron microscopy in the era of molecular genetics. The emphasis is on genotype/glomerular phenotype correlations.     

A Primary Pleural Tumor

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.     

Aorticopulmonary Paraganglioma (Aortic Body Tumor): Report of a Case

A case of aorticopulmonary paraganglioma in a 57-year-old man is described. The tumor comprised nests of uniform cells in a fibrovascular stroma. Electron microscopy revealed abundant neurosecretory granules, and S-100 protein staining demonstrated scattered sustentacular cells at the periphery of typical zellballen. The findings in this case correlated with those of studies on the prognosis for extraadrenal paragangliomas.     

Cytokeratin-Containing Globular Filamentous Bodies in Renal Oncocytoma

Eighty-four cortical neoplasms were studied for cytokeratin and vimentin expression by immunohis-tochemistry and for intermediate filament aggregates by electron microscopy. Twenty oncocytomas expressed cytokeratin, 16 in a distinctive punctate pattern. These same 16 tumors also contained small globular filamentous bodies (GFB) by electron microscopy. The GFB were characterized by a matrix of intermediate-sized filaments with incorporation of diverse cell organelles such as endoplasmic reticulum, lysosomes, mitochondria, and lipid. The GFB were not within a unit membrane. Although 11 of 64 carcinomas also contained intermediate filament aggregates, only 2 of these solely expressed cytokeratin, and this was restricted to a few cells in small foci. Small GFB were also present in 5 carcinomas by electron microscopy. Three mixed clear and granular cell carcinomas contained only rare cells, whereas 2 sarcomatoid carcinomas, both of rhabdoid cell phenotype, contained numerous GFB that coexpressed vimentin and cytokeratin. Cytokeratin-containing GFB are common in oncocytomas but are uncommon in carcinoma, and, when numerous, may provide a diagnostically useful immunohistochemical feature with which to distinguish oncocytoma from its carcinoma congeners.     

Cell Interposition in Glomerular Capillary Walls in Cryoglobulinemic Glomerulonephritis (CRYGN). Ultrastructural Investigation of 23 Cases

The present report describes ultrastructural findings on twenty-three cases of CRYGN showing membranoproliferative pattern under light microscopy. Attention was paid to the presence of double contoured peripheral basement membranes and to the characteristics of the interposed cells. The latter, according to the well known characteristics of membranoproliferative GN, are thought to be mesangial in nature. In fact, mesangial cells were found in 8 cases only, always associated with monocytes. Only monocytes were recorded in 12 cases, whereas in other 3 cases double contours were not connected to cell interposition.

Despite similarities under light microscopy, CRYGN is therefore rather different from idiopathic membranoproliferative GN because of the prevalence of exudative changes, mainly due to monocyte infiltration, over proliferative lesions.     

Ultrastructural Heterogeneity in Malignant Fibrous Histiocytoma of Soft Tissue

Five soft tissue sarcomas with histological features of malignant fibrous histiocytoma were selected to illustrate their ultrastructural heterogeneity. One case displayed the mixture of fibroblastic and histiocytic cells characteristic of the majority of malignant fibrous histiocytomas. In 1 case the tumor was composed entirely of primitive mesenchymal cells. The other 3 cases showed lipogenic, neurogenic, and “granular-cell” differentiation, respectively. These findings emphasize the important role of electron microscopy in the precise diagnosis and classification of malignant fibrous histiocytoma.