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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Lung tumors were induced in female Syrian golden hamsters by intratracheal instillation of benzo[a]pyrene-Fe2O3. The tumors were characterized with the use of coordinated morphologic and histochemical techniques including electron microscopy. The lung carcinomas were classified according to their presumed cell of origin. Most were derived from mucous cells and/or basal cells, and they were classified as either epidermoid carcinomas or as combined epidermoid and adenocarcinomas. The tumors in the second group (57% of the total number of carcinomas) presented a wide spectrum of epidermoid and adeno components. The epidermoid component was characterized in well-differentiated tumors by the presence of intercellular bridges and/or keratinization. Well-developed desmosomes and numerous bundles of tonofilaments were observed ultrastructurally. In diagnosing adenocarcinoma, one no longer needs to depend on the presence of tubules or gross glandular structures as criteria for diagnosis. The presence of intracellular and/or extracellular alveoli, well-developed Golgi complex, and endoplasmic reticulum and/or evidence of mucous secretion provide more definitive criteria. A tumor composed of neurosecretory cells that morphologically resembled a bronchial carcinoid of man was observed. Nests of uniform, small, polygonal cells with round-to-oval nuclei were seen at the light microscopic level. Dense-core secretory granules 1,100-2,200 A were present in the cytoplasm of the tumor cells. Several fibrosarcomas were observed. The tumors showed a very cellular structure, composed of either densely packed ovoid or spindle-shaped cells. Ultrastructurally, the cells resembled fibroblasts. The results obtained in this study give strong support for a histogenetic classification, i.e., a classification based on the cell of origin.
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PMID:The respiratory epithelium. VI. Histogenesis of lung tumors induced by benzo[a]pyrene-ferric oxide in the hamster. 35 53

Immunoblastic lymphosarcoma (ILS) is a newly recognized malignant lymphoreticular neoplasm and is included in the recent W.H.O. classification of lymphomas. This report concerns six cases of ILS studied by light, immunofluorescence (IF), and electron microscopy (EM). Four patients were female and all except one were over 50 years of age. Four patients had some immunological abnormality. Light microscopy showed a monomorphic population of immunoblasts with pyroninophilic cytoplasm and variable plasmacytoid differentiation. Intracytoplasmic IgG was demonstrated by IF in four cases, and IgA in one. Large lymphoid cells with varying proportions of polysomes, rough endoplasmic reticulum, and Golgi apparatus were seen by EM in four cases. Mean survival was 4.8 months in five cases; death in four was due to disseminated ILS. We concluded that our cases of ILS are of B cell origin, are often associated with immunological abnormalities, and carry a poor prognosis. Immunofluorescence and EM are helpful in its diagnosis.
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PMID:Immunoblastic lymphosarcoma: a light, immunofluorescence, and electron microscopic study. 36 67

Neither immunologic nor genetic concepts of carcinogenesis have yet been decisively confirmed, and epigenetic theories, as formulated so far, are either non-predictive or insufficiently consistent with morphologic and experimental evidence. Computing data, concerned with carcinogenic mechanisms and neoplastic changes at the level of the endoplasmic reticulum, may lead to a new coherent understanding of tumor pathogenesis. Carcinogenic agents initiate biophysical perturbations, chemical alterations and conformational transitions in the membrane lattice of the endoplasmic reticulum. Foremost among the resulting neoplastic changes is an increased, irreversible separation of polyribosomes from membranes of the ergastoplasm. The carcinogenic process, apparently, deletes a protein required for polysome attachment. Since microsomal cytochromes can be synthesized by membrane-bound polysomes only, the translation of genetic information for their biosynthesis is irreversibly restricted. A similar, self-perpetuating deficiency may be postulated for the polysome attachment protein. Activities, depending on cytochromes P-450 and b5, are hampered, e.g. those of the monoxygenase system. Cholesterogenesis is derepressed. Ratios of phospholipids/cholesterol are decreased, and lipid-protein complexes, altered both in structure and function. Another distinct effect of the membrane-polysome separation is the unmasking of thiol-disulfide exchange enzymes which, in turn, stimulate the biosyntehsis of proteins and of deoxyribonucleotides involved in cell replication.
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PMID:Microsomal aspects of carcinogenesis and neoplasia. 37 54

Implantation of 7,12-dimethylbenz(a)anthracene (DMBA) into the pancreas of rats has been shown to induce adenocarcinoma. Complexes of tubules, which have the appearance of proliferated intralobular ducts, frequently appear during tumor development. These complexes were studied by light and electron microscopy to determine their method of formation. In addition, a tubular complex was reconstructed from serial sections to determine its three-dimensional configuration. Although tubular complexes have been thought by others to result from ductal proliferation, the following observation indicate that they originate from zymogen-granule-containing cells: a) there is a continuum of transitional stages between acini and tubules, b) most tubules decrease in size and are replaced by connective tissue (evidence of regression rather than proliferation), c) few mitotic figures are seen in tubular complexes, d) the tubules comprise many cells which have an abundance of rough endoplasmic reticulum, an organelle which is sparce in ducts, and e) the three-dimensional arrangement of tubules appears identical to the branching, anastomosing arrangement of zymogen-granule-containing cells of the normal rat pancreas. Control animals in which only sutures were placed in the pancreas showed minimal reaction. It is concluded that "acini" become recognized as tubules when loss of zymogen granules accompanies tumor induction by DMBA. Transformation of these cells could be erroneously interpreted as transformation from proliferating ducts.
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PMID:Origin of tubular complexes developing during induction of pancreatic adenocarcinoma by 7,12-dimethylbenz(a)anthracene. 41 16

Intracytoplasmic membranous structures, known as annulate lamellae were seen in a malignant mesenchymal tumor. Close relationship with rough endoplasmic reticulum (ER) suggested their origin from ER.
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PMID:Annulate lamellae in a malignant mesenchymal tumor. 41 87

Four cases of anaplastic carcinoma of the thyroid, composed of one small cell carcinoma and three giant cell carcinomas, were studied with electron microscope. In the case of small cell carcinoma, fine cytoplasmic interdigitations and junctional complex between apposing cytoplasmic membranes of neighbouring tumor cells and a few microlumina within tumor cell clusters surrounded by well-defined basal lamina were seen. In the cases of giant cell carcinoma, occasional cytoplasmic interdigitations as well as desmosomal structures were detected even in tumor cells markedly pleomorphic and anaplastic. Abundant cytoplasmic organelles including profiles of Golgi apparatus, rough endoplasmic reticulum and a few mitochondria were seen in the cytoplasm of tumor cell of all four cases. Of interest to note was that all giant cell carcinomas demonstrated evidences of fairly well differentiated tumor within anaplastic carcinoma, indicating probable pre-existing either benign or malignant epithelial neoplasm more differentiated, with its subsequent anaplastic transformation. Findings in the present study support an assumption that these anaplastic tumors are derived from the follicular epithelium of the thyroid gland. In addition, it can be said that tumor cells of the small cell carcinoma provide evidences suggesting functional differentiation of carcinoma cells to a certain extent, yet unable to produce thyroglobulin.
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PMID:Anaplastic carcinoma of the thyroid gland. An ultrastructural study on four cases. 43 88

A quantitative ultrastructural investigation of cancer in mice mammary glands and of its metastases to the lungs was carried out. It was established that in tumors showing no metastatic spreading in experiment the area of membrane surface of the endoplasmic reticulum and the number of bound ribosomes are greater than those in tumor spreading metastases. At the same time the number of ribosomes organized into polysomes is higher in the metastasized tumors. The comparison of the tumors with their metastases revealed differences in the structure of the mitochondrial apparatus: the surface area of cristae is larger in the metastatic foci. The evidence obtained shows that tumors spreading metastases have a lower level of cellular differentiation. The primary and metastatic foci do not exhibit any difference in the level of differentiation.
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PMID:[Relation of the ultrastructural organization of mouse mammary gland cancer to its ability to metastasize]. 43 24

Annulate lamellae have been found in a primitive neuroectodermal tumor, a metastatic cerebellar tumor, a testicular seminoma, a retinoblastoma and three melanomas. These annulate lamellae are arranged in stacked parallel arrays in the cytoplasm of tumor cells. The number of annulate lamellae observed to comprise a single stack varies from 2--4 in the seminoma tumor to 5--18 in the cerebellar tumor. Although the functional significance of annulate lamallae is still unknown, in many instances they have been found to be continuous with rough-surfaced cisternae of the endoplasmic reticulum and ribosomes have been demonstrated on the surface of annulate lamellae. This may suggest that annulate lamellae participate in protein synthesis.
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PMID:Annulate lamellae in human tumor cells. 45 90

The ultrastructure of benign osteoblastoma of the maxilla in a 14-year-old boy was studied. Morphologically, the tumor tissue was composed of abundant osteoid of a trabecular form, and cellular and vascular connective tissue. The cellular components were osteoblasts, osteoclasts, osteocytes entrapped within the osteoid, and small perivascular cells of two types. The small cells of one type were ovoid and had a relatively large nucleus and a dark cytoplasm. The cells of the other type were elliptical and had a clear cytoplasm. The former seemed to be a preosteoblast and the latter could not be identified. The osteoblast was the predominant cell in this lesion and was characterized by the presence of abundant rough-surfaced endoplasmic reticulum and several Golgi complexes. These characteristics indicated the pronounced activity of collagenous fiber synthesis and the matrix of the osteoid tissue.
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PMID:Ultrastructural study of benign osteoblastoma of the maxilla. 49 97

The ultrastructure of a human pineoblastoma is described. Tumor cells formed nests, palisading row and rosettes. Cells within nests were undifferentiated. Palisade and rosette forming cells had polarized cytoplasms and showed signs of differentiation and surface membrane specialization which included surface end-bulb-like protrusions of the cytoplasm, bulbous cilia with a 9 + 0 microtubular skeleton, and blunted microvilli. In the cytoplasm of tumor cells there were characteristic granular bodies, whorls of smooth endoplasmic reticulum and annulate lamellae. Some of these findings appear to be unique to pineal tumor and are reminiscent of photoreceptor cells in the pineal glands of lower vertebrates and human fetal pineal glands.
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PMID:Pineoblastoma: an electron microscopic study. 49 40


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