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K Hewan-Lowe

Publications and source records attributed to K Hewan-Lowe.

36 records · Page 2Linked to original sources
PubMed1991

In situ oncocytic change in association with multiple renal cell adenocarcinomas.

We report a case of in situ oncocytic change in association with two low-grade renal cell adenocarcinomas and one contralateral low-grade oncocytic adenocarcinoma. The in situ oncocytic change showed abundant cytoplasmic mitochondria confirmed by ultrastructural examination and phosphotungstic acid-hemotoxylin staining. In addition, this in situ oncocytic change expressed cytokeratin CAM 5.2 in the absence of cytokeratin AE1/AE3, as reported in oncocytic renal cell adenocarcinomas. Further study of in situ oncocytic change identified in kidneys resected for adenocarcinomas with regard to follow-up and management of the contralateral kidney seems indicated.

Carcinoma↗
PubMed1990

Primary pulmonary alpha-fetoprotein-producing malignant germ cell tumor.

We are reporting the clinical and pathologic features of a primary, pulmonary, malignant germ cell tumor associated with a marked elevation of serum alpha-fetoprotein (38,427 ng/mL) and lactate dehydrogenase activity (756 U/L), in a 26-year-old female. This controversial, rare neoplasm has not been extensively discussed in the pathology literature. We emphasize the clinical importance of establishing this diagnosis in view of the favorable response to chemotherapy shown by malignant germ cell tumors.

Adult↗
PubMed1984

Ultrastructure and immunohistochemical localization of estradiol in three thecomas.

Three ovarian thecomas were studied by ultrastructural and immunohistochemical techniques. In each tumor, a small number of tumor cells stained for estradiol. Vacuolated as well as plump non-vacuolated tumor cells were positive, but spindle-shaped cells were negative. Ultrastructural examination showed two principle cell types. Type I cells were immature mesenchymal cells that differed from typical steroid-secreting cells because only a minority had conspicuous smooth endoplasmic reticulum, although mitochondria often had tubular cristae. Type II cells were distinguished by abundant intermediate (10-nm) microfilaments and round mitochondria with incomplete cristae and empty centers. Focal smooth muscle differentiation was present in each tumor. Adherens-type intercellular junctions, including desmosomes in one case, and degenerate cells with markedly vesiculated cytoplasmic membrane systems were also present. Lipid was not abundant, but it was more conspicuous in degenerate cells and in type II cells. Thecoma cells thus closely resemble both ovarian stromal cells and theca interna cells, which are known to be capable of steroidogenesis. The localization of estradiol in a minority of tumor cells in each thecoma suggests that thecoma cells, too, are capable of steroid synthesis and supports the popular concept that hyperestrogenism in patients with thecomas may be the result of estradiol secretion by these tumors.

Adolescent↗
PubMed1979

Predictive values of thyroxine, thyrotropin, and triiodothyronine concentrations in serum.

The predictive values of total thyroxine, thyrotropin, and total triiodothyronine concentrations in serum for clinically apparent and subclinical hypothyroidism and hyperthyroidism were determined by retrospective analysis of clinical cases chosen from the frequency distributions of hormone test results. Very low total thyroxine concentrations, less than 25 microgram/L, were specific for hypothyroidism. Most subclinical hypothyroid cases had intermediate or low total thyroxine concentrations, 35-60 microgram/L, with moderately increased thyrotropin concentrations, greater than 12 milli-int. units/L. Thyrotropin cut-off concentrations were identified that had predictive values greater than 90% for classifying untreated and hormone-treated hypothyroid cases. Above-normal total thyroxine concentrations, regardless of absolute value, were not specific for hyperthyroidism, because binding-protein alterations related to estrogen taking were prevalent and produced occasional marked increases in serum total thyroxine. Nevertheless, cut-off concentrations for serum total thyroxine and total triiodothyronine were identified that had a predictive value greater than 90% for hyperthyroidism, without necessitating measurement of the capacities or concentrations of hormone-binding proteins.

Adolescent↗
PubMedDate not supplied

Vasculopathic changes of CADASIL can be focal in skin biopsies.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a newly described cause of vascular dementia. Pathologic examination shows multiple small infarcts in the deep cerebral white matter together with a nonatherosclerotic, nonamyloid angiopathy involving the media of small cerebral arteries. Ultrastructurally, characteristic granular material is present in the basal lamina of vascular smooth muscle cells in cerebral and extracerebral blood vessels. The ultrastructural changes have also been demonstrated in skin biopsies of affected patients; consequently, some investigators have recently recommended skin biopsies for the diagnosis of CADASIL. This study describes a 54-year-old male with a family history for strokes who had clinical and radiological features suggestive of CADASIL. A skin biopsy was performed to confirm the diagnosis. Initially, the characteristic vasculopathic changes of CADASIL were not identified within small blood vessel walls. However, multiple deeper sections in other areas showed electron-dense material associated with vascular smooth muscle cells, characteristic of CADASIL. Subsequent genetic testing demonstrated a single nucleotide substitution at position 659 on chromosome 19p13.1 causing an amino-acid change (Cys --> Phe), a finding indicative of CADASIL. The involvement of blood vessels within the dermis makes skin biopsy a useful adjunct in the diagnosis of CADASIL. However, as illustrated by this case, the findings may be focal, requiring a thorough evaluation of the entire biopsy specimen.

Biopsy↗
PubMedDate not supplied

Ovarian myxoma: ultrastructural and immunohistochemical findings.

The ultrastructural and immunohistochemical findings are reported in two ovarian myxomas, one of which was also associated with a sclerosing stromal tumor of the same ovary. Both neoplasms showed a myxoid, moderately cellular proliferation of spindle and stellate cells interspersed with areas of fibrosis and hemorrhage as well as delicate vascular spaces. Ultrastructurally, stellate neoplastic cells with irregular nuclei and occasional nucleoli were embedded in a mucinous and loose collagen matrix. Their cytoplasm showed abundant intracytoplasmic thin filaments that rarely condensed into poorly formed dense bodies. These thin filaments correlated with immunoreactivity for muscle-specific actin and vimentin. The neoplastic cells showed no immunoreactivity with antibodies to desmin, S-100 protein, cytokeratin AE1:AE3, factor VIII-related protein, or placental alkaline phosphatase. These ultrastructural and immunohistochemical findings are consistent with myofibroblastic differentiation. These ancillary studies exclude important, clinically more aggressive differential considerations such as myxoid rhabdomyosarcoma, myxoid liposarcoma, myxoid neural tumors, mucinous adenocarcinoma showing pseudomyxomatous change, and myxoid-appearing endodermal sinus (yolk sac) tumor.

Actin Cytoskeleton↗
PubMedDate not supplied

Microcomputer application: an image database system for electron microscopy.

An electron microscopist in a small electron microscopy laboratory that processes 200 cases per year can generate at least 2000 electron micrographs within this time period. These electron micrographs are stored in filing cabinets, which slowly encroach on existing laboratory space. Related image data are often located in separate filing systems. This type of storage system is inefficient for rapid retrieval of sets of electron micrographs for research, teaching, or retrospective review of patient material. An electron microscopy image base, which is implemented on a microcomputer, can provide flexible and simultaneous access to both digitized electron micrographs and their relevant textual data. In addition to the advantage of more efficient retrieval, electronic storage of textual data and digitized electron micrographs also offers the advantage of decreased storage space for this type of data. Implementation of the initial version of the electron microscopy image base demonstrated that future versions must provide improved resolution of the digitized electron micrograph and sufficient electronic mass storage to support such a large image base. Ongoing developments in database technology and mass storage make it worthwhile to pursue additional refinements of the electron microscopy image base.

Database Management Systems↗
PubMedDate not supplied

Diagnostic electron microscopy: future development.

When the electron microscope was initially developed, pathologists thought that it would become the ultimate diagnostic tool for tumor diagnosis because the structure of subcellular organelles could be visualized. However, the role of diagnostic electron microscopy in tumor diagnosis diminished rapidly when it was noted that there were a finite number of diagnostic subcellular organelles and that immunohistochemistry could yield the answer to questions which related to tumor diagnosis more rapidly and cheaply. If diagnostic EM is to remain a viable entity, its future role in tumor diagnosis lies in exploiting the relevance of the correlation between structure and function of subcellular organelles. This correlation between structure and function of subcellular organelles is best accomplished in an environment in which the recent technologic advances in electronics are incorporated into the electron microscopy laboratory.

Clinical Laboratory Techniques↗
PubMedDate not supplied

Leiomyosarcoma of the upper extremity.

A case of rapidly fatal, high-grade leiomyosarcoma of the upper extremity is described. The pleomorphic appearance of this sarcoma on light microscopy required the use of immunohistochemistry and electron microscopy to establish the morphologic diagnosis and to exclude a diagnosis of other high-grade sarcoma, such as malignant fibrous histiocytoma or pleomorphic rhabdomyosarcoma. The observed clinical behavior of this leiomyosarcoma of the upper extremity seemed unusually aggressive compared with the biologic behavior predicted by the independent prognostic indicators of location, tumor size, and depth of invasion. The observed clinical behavior did not seem unusual compared with the clinical behavior predicted by the use of a staging scheme for soft tissue sarcomas.

Arm↗
PubMedDate not supplied

Perineurial cell differentiation in benign tumors and tumorlike proliferation of peripheral nerves.

An unusual, benign, spindle cell peripheral nerve sheath tumor (PNST) is reported that on ultrastructural examination was composed only of perineurial cells. The neoplastic cells showed positive immunoreactivity for S-100 protein and negative immunoreactivity for epithelial membrane antigen; this is not the expected immunophenotype of a perineurioma. Continued examination of benign PNSTs using electron microscopy and immunohistochemistry has the potential to reveal additional variations in the cellular composition and immunophenotype of these soft tissue tumors. PNSTs such as the one described will renew the debate about the cytogenesis of the perineurial cell and its role in PNSTs.

Adult↗
PubMedDate not supplied

Polyvinylpyrrolidone storage disease: a source of error in the diagnosis of signet ring cell gastric adenocarcinoma.

False-positive and false-negative diagnoses of cancer seldom occur during evaluation of gastric mucosal biopsy specimens obtained during flexible fiberoptic endoscopy of the stomach. When they do occur, false-negative diagnoses are usually the result of undersampling of the lesion, whereas false-positive diagnoses are the result of overinterpretation of benign histologic lesions. The diagnosis of diffuse signet ring cell adenocarcinoma is associated with both false-positive and false-negative diagnoses of cancer. The signet ring cell can be easily overlooked. Mucicarminophilic cells can be overinterpreted as diffuse signet ring cell adenocarcinoma. Polyvinylpyrrolidone is an unusual cause of this type of false-positive diagnosis of gastric adenocarcinoma. Judicious use of histochemical stains, immunohistochemistry, and electron microscopy plays a significant role in avoiding the false-positive diagnosis of diffuse signet ring cell adenocarcinoma.

Biopsy↗
PubMedDate not supplied

Ultrastructural distinction of basaloid-squamous carcinoma and adenoid cystic carcinoma.

Basaloid-squamous carcinoma is a unique and infrequent variant of squamous cell carcinoma with a predilection for occurring in the upper aerodigestive tract. The cardinal diagnostic criteria are the presence of basaloid cells arranged in lobules or cords and a squamous component. Another feature that distinguishes basaloid-squamous carcinoma from conventional squamous cell carcinoma is the development of multiple foci of amorphous, eosinophilic, or mucinous materials among the basaloid tumor cells. It is this feature in basaloid-squamous carcinoma that causes confusion with adenoid cystic carcinoma, especially the solid variant of adenoid cystic carcinoma. To clarify the distinctive features of these two types of tumors, the ultrastructural findings in three basaloid-squamous carcinomas from the head and neck region were compared with three adenoid cystic carcinomas, one from the head and neck region and one each from trachea and bronchus. Widened intercellular spaces, tonofilaments, and replicated basal lamina were present in both types of tumor. However, the ultrastructural features of glandular differentiation were present only in adenoid cystic carcinoma, whereas the ultrastructural features of squamous cell differentiation were present only in basaloid-squamous carcinoma. The distinction between basaloid-squamous carcinoma and adenoid cystic carcinoma is important since basaloid-squamous carcinoma is a clinically aggressive, high-grade form of squamous cell carcinoma, generally with a worse prognosis than adenoid cystic carcinoma.

Adult↗