Electron microscopic findings in four cases of nasopharyngeal fibroma

Electron microscopy of juvenile nasopharyngeal angiofibroma: clinical and histopathological correlates

BACKGROUND

The histological and electron-microscopic (EM) characteristics of juvenile nasopharyngeal angiofibroma (JNA) have been described but no study has compared them with one another or with clinical features. The objective is to compare ultrastructural characteristics of JNA with clinical parameters.

METHODS

This prospective study included histology of 21 samples of which only 13 underwent transmission-EM. Four clinical parameters (age, duration, epistaxis, recurrence), three radiological-staging, 13 histological and 15 EM characteristics were considered. A descriptive analysis for association of these characteristics and also with clinical parameters was attempted. Furthermore statistical analysis of clinical and radiological categories with respect to frequencies of ultrastructural characteristics was also undertaken.

RESULTS

Dense-intranuclear-inclusions (DNI) and peripheral-nuclear-irregularities were universally encountered while other very prominent features were nuclear-blebs-and-pockets, myoid-features, thin-vessel-wall (TnVW), irregular-vascular-contour (IVC) and fibrous-stroma (FS). Statistical significance was obtained between recurrence with histology (p = 0.04) and Fisch staging with EM (p = 0.001). While muscle-in-vessel-wall, thick-vessel-wall, mast-cells, stellate-stromal-cells and cellular-stroma predominated in recurrent cases, the upfront disease showed predominance of scar-like-stroma, fusiform-stromal-cells, IVC, TnVW, FS, organised-collagen-bundles and less-cellular-stroma. A very unique Rod-like-structures were appreciated in the cytoplasm of the fibroblast for the first time.

CONCLUSIONS

While histological parameters of recurrence need further validation, a larger sample may better define histopathological surrogate for predicting intracellular dynamics that may further correlate with underlying cellular stresses. Hence an 'ultrastructural staging' may better customise treatment protocol and prognosis. Furthermore 'characteristic' unique rods need to be further investigated along with validation of viral aetiology for DNI.

Expression of CD34-antigen in nasopharyngeal angiofibromas

Formalin-fixed, paraffin-embedded and frozen tissues of 24 patients with primary nasopharyngeal angiofibroma, of whom seven had recurrences, were studied immunohistochemically for the expression of CD34 antigen using two different antibodies (HPCA-1 and QBEND 10). In all cases, there was an exclusive staining of endothelial cells, while pericytes, smooth muscle cells and stromal fibroblasts were not reactive. The staining intensity, however, was more pronounced in small tumor vessels of capillary- and sinusoidal-type than in larger vessels, which were usually characterized by an irregular smooth muscle coat. This differential staining indicates an increased proliferative potential of the endothelium of the small vessel component of nasopharyngeal angiofibroma (neoangiogenesis) and an inhibitory influence of vascular smooth muscle cells on endothelial cell growth. Moreover, the positive immunoreaction of all endothelial cells for CD34 is indicative of the absence of lymphatic vessels, which confirms previous ultrastructural observations. No differences in the staining pattern were observed between primary versus recurrent tumors, formalin fixed, paraffin embedded versus snap-frozen acetone fixed material, or between both CD34 antibodies. Our findings indicate that nasopharyngeal angiofibroma is a vasoproliferative malformation.

Nasopharyngeal angiofibroma: an immunohistochemical study of 32 cases

Thirty-two cases of nasopharyngeal angiofibroma, including 2 recurrences, all of which had been excised from males between 7 and 25 years, were subjected to systematic immunohistochemical study. Most of the tumour vessels, which lacked elastic laminae, were characterized by vascular walls of irregular thickness and variable muscle content. In places endothelial cells were only separated from the stroma by a single attenuated layer of contractile cells, whereas elsewhere the same vessel walls showed pad-like thickenings of their muscle coat. All cells of the vessel walls showed immunoreactivity for vimentin and smooth muscle actin, whereas desmin-positive cells were present only in small numbers in some vessels, generally those with thicker muscle coats. The stromal cells were decorated by vimentin antibodies only; however, in some more fibrotic hyaline areas the stromal cells displayed also reactivity for smooth muscle actin. In most cases S-100 protein-staining disclosed many nerves, and this accentuated their parital distortion by tumour tissue. Our findings provide an extended insight to the morphology of angiofibromas at this site, particularly highlighting the irregularity of their vascular walls, which, taken together with the lack of elastic laminae and elastic stromal fibres, can be held responsible for the typical pronounced tendency for haemorrhage in these lesions.

Juvenile angiofibroma of the maxillary sinus. A case report

The clinicopathological features of a rare case of juvenile angiofibroma originating from the maxillary sinus of a 13-year-old boy are reported. This tumor was composed of angiomatous and fibrous structures. The analysis of nucleolar organizer regions (NOR) of the various components of this tumor indicated that the fundamental elements were the fibroblastic cells, rather than the vascular endothelial cells.

Apposition of fibroblasts to mast cells and lymphocytes in normal human lung and in cryptogenic fibrosing alveolitis. Ultrastructure and cell perimeter measurements

The perimeters of mast cells and lymphocytes in human lungs were measured in electron micrographs by digitizer to determine the percentage of perimeter apposed to fibroblast (PPAF). Fibroblasts were apposed to the majority of mast cells. The median PPAF for mast cells in normal lung was 50.3 per cent, and in cryptogenic fibrosing alveolitis (CFA), 35.7 per cent. Although the value in CFA was lower, the difference was not statistically significant (median difference 11.8; 95 per cent confidence interval (-19.6, 25.1); P = 0.65). The PPAF range overall was 3.8-94.1 per cent. There was similar apposition of fibroblasts to lymphocytes, and no statistical differences were found when median PPAF results for mast cells and lymphocytes were compared for normal and CFA lung. The high degree of percentage apposition, accurately quantified in this study, shows that fibroblasts, mast cells, and lymphocytes are ideally arranged structurally in normal alveolar walls, to facilitate the many physiological interactions which are currently being uncovered. The present study also shows that apposition persists in pathological states, e.g., CFA lung, but because all these cells are increased in number in CFA lung, apposition is easier to identify here than in normal lung.

Linear arrays of homogeneous mast cells in the dura mater of the rat

Using fluorescence histochemistry, 5-HT, histamine and heparin were colocalized in a large population of cells in the dura mater thereby identifying them as mast cells. In addition, because these cells were highly sensitive to compound 48/80 and were densely packed with granules of a consistent density, they were identified specifically as 'connective tissue' mast cells. Other types of mast cells, i.e. 'mucosal' or 'neurolipomastocytes', were not present in the rat dura mater. 5-HT immunohistochemistry was the best technique for demonstrating that there were populations of mast cells, one associated with each of the two layers of dura. Although shaped differently the type of mast cell in each layer was the same. It was observed that mast cell shape is dependent on the contiguity, density and orientation of its surrounding elements, not its type. In general, mast cells in the outer layer were aligned parallel to the middle meningeal artery and those in the inner layer were parallel to trigeminal nerve branches that coursed obliquely across the middle meningeal artery. Examination of cross-sections of dura revealed that most mast cells also were aligned at the interface between the two dural layers. The linear orientation of mast cells in two planes of each layer suggests a programmed lamellar seeding of these cells during development of the dura. This study also demonstrated that the majority of dural mast cells were more closely related to other connective tissue elements than to blood vessels and nerves. These results (1) are compatible with the suggestion that dural mast cells play a non-obligatory role in the neuroinflammatory response, (2) leave open to question the role of the dural mast cell in headache or the regulation of blood flow, and (3) support evidence that dural mast cells play an important role in connective tissue related functions, e.g. development, inflammatory response to injury and wound repair.

Interaction between mast cells and perineurial fibroblasts in neurofibroma. New insights into mast cell function

Transmission electron microscopy was performed on seven neurofibromata to study the relationship between the frequently occurring mast cells and the other cell types present in the tumour. Intimate association was observed between mast cells and perineurial fibroblasts, but not between mast cells and Schwann cells. At the contact interface between mast cells and perineurial fibroblasts, numerous vesicle-like structures were observed with corresponding endocytotic vesicles in the fibroblast plasma membrane. The authors regard this close morphological relationship as in vivo evidence for a possible role of mast cells in fibroblast metabolism, a conclusion which has already been drawn from in vitro studies, but until now inadequately supported by observations in vivo.

Phagocytosis of mast cell granules by fibroblasts of the human gingiva

Mast cell granules have been detected ultrastructurally within the cytoplasm of fibroblasts in fibrous hyperplastic lesion of the human gingiva. This finding is interpreted as phagocytosis of mast cell granules by fibroblasts. It is estimated that phagocytosis of mast cell granules occurred in four to six per cent of the fibroblasts. The result of present study suggests that mast cells play some role in fibroblast activity not only in animals as reported previously, but also in human connective tissue.

A novel cell-to-cell interaction between mast cells and other cell types

Time-lapse cinephotomicrography and transmission electron microscopy (TEM) have been used to study the interactions between rat mast cells and different cell monolayers in culture (fibroblasts, vascular endothelial cells and cardiac muscle cells). This report documents a novel form of behavior between mast cells and certain other cell types. We have tentatively termed this cellular behavior 'transgranulation', which involves sequential changes not seen in control cells, including: (1) formation of a granule-containing mast cell pseudopod that becomes closely applied to an adjacent cell; (2) development of specialized plasma membrane interrelationships between apposing cells; (3) alteration of granules and perigranular membranes within the mast cell pseudopod; (4) occasional transfer of exocytosed mast cell granules to the cytoplasm of the adjacent cell; (5) presence of a specialized inclusion body in the mast cell; and finally, (6) either withdrawal of the pseudopod by the mast cell, or casting-off of the pseudopod from the mast cell, leaving it on the surface of the adjacent cell (pseudopod translocation). These mast cell interactions occur specifically with fibroblasts and endothelial cells in vitro and are never observed with cardiac muscle cells or non-cellular substrates. Our investigations of rat mesenteries in situ confirm that these cell-cell interactions also occur in vivo. We suggest it represents a form of cell-to-cell communication involving secretion from a mast cell pseudopod to another cell type. The significance of specialized contacts between mast cells and other cell types in vivo is discussed.

Electron microscopy in surgical pathology: a selective review

The high resolution provided by electron microscopy can contribute to histomorphological diagnosis by allowing the detection of structures which are invisible to the light microscope. These structures include characteristic nuclear or cytoplasmic contours, intercellular attachments and intracellular components. The recognition of such features may allow specific diagnosis in lesions which cannot be precisely categorized by light microscopy. Electron microscopy is particularly useful for the diagnosis of neoplasms. This review describes some of the characteristic morphological features which can be demonstrated in neoplastic cells by electron microscopy and briefly considers several areas where the technique is of special value. Electron microscopy is now an integral part of the diagnostic process in surgical pathology and can be regarded as a routine technique rather than a special procedure to be delegated to others.

Light and electron microscopic investigations of nasopharyngeal carcinomas with regard to the viral etiology of these tumors

Five carcinomata of the nasopharynx (four lymphoepithelial carcinomata of the Regaud type and one squamous cell carcinoma) were examined light and electron microscopically. In addition to the familiar histological and cytological features of these tumors, and because of an increased antibody titer against Epstein-Barr virus in all five patients, all those cytoplasmic and nuclear inclusions were examined which could be interpreted as indicative of a virus contact. The following structures were found: 1. Particles and microtubules which correspond in diameter, shape, and location to Corona viruses. 2. Particles surrounded by a double membrane and resembling in form and diameter Oncorna viruses. 3. Tubulo-reticular, coil-shaped cytoplasmic inclusions interpreted as an unspecific reaction of the host cell to viral attack. 4. Spherical nuclear bodies, which are frequently observed in tumors and in viral infections. 5. Intranuclear particles which correspond in diameter, structure, and distribution to viruses of the herpes type such as have been described in cell cultures of Burkitt lymphoma and nasopharyngeal carcinoma. The fifth group particularly was discussed in detail with regard to differentiation between those particles and other structures which could simulate a virus structure. Together with the appearance of increased ribosomes and of particular chromatin distribution within the tumor cell nuclei, the particles we discussed have been interpreted as morphological indications of a virus etiology of the examined tumors.