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S T Yuen

Publications and source records attributed to S T Yuen.

At least 73 records · Page 4Linked to original sources
PubMed1997

Monocyte chemoattractant protein-1 expression and macrophage infiltration in gliomas.

While the number of reports on macrophage infiltration of gliomas is increasing, the extent and mechanisms of macrophage recruitment remain unclear. To investigate whether monocyte chemoattractant protein-1 (MCP-1) plays a role in this process, in situ hybridisation (ISH) was performed for 22 glioblastomas (GBM), 1 anaplastic astrocytoma (AA) and 4 grade II fibrillary astrocytomas (AII) and reverse transcription-polymerase chain reaction was performed in 13 GBM, 1 AA and 3 AII. High levels of MCP-1 mRNA were detectable in most GBM, while a lower level was detected in AII. Many tumour-associated macrophages (TAM) could be demonstrated by immunohistochemistry (IHC) in most GBM, while the AII contained a lower number of TAM. The positive correlation between the MCP-1 level and abundance of TAM suggested that MCP-1 has a role in TAM recruitment. By combining ISH and IHC, high levels of MCP-1 mRNA were shown both in tumour cells and TAM. Along tumour borders, reactive astrocytes and microglia also expressed MCP-1. In areas with T lymphocyte infiltration, larger numbers of MCP-1-positive cells with an enhanced level of expression could be identified. We propose that the mechanism of macrophage recruitment is, at least partly, effected by constitutive expression and T cell-mediated up-regulation of MCP-1 in tumour cells and TAM. The production of MCP-1 by TAM establishes a positive amplification circuit for macrophage recruitment in gliomas.

Astrocytoma↗
PubMed1997

Colorectal carcinoma in Hong Kong: epidemiology and genetic mutations.

The incidence of colorectal carcinoma is rising at an alarming pace in Asian urban societies such as Hong Kong. Detailed examination of the epidemiological pattern and genetic mutation of colorectal cancer in the Hong Kong Chinese population is overdue. We compared the reported age incidence of colorectal carcinoma in Hong Kong with that of Scotland and other countries. Hong Kong showed a much higher incidence of colorectal carcinoma among the young age groups. By comparison with other countries, this raised incidence among the young appeared to be related to southern Chinese societies. The recent dramatic rise in colorectal cancer in Hong Kong was largely attributable to an increase in the over 50 years age group, while the young incidence remained unchanged. We also defined the mutation spectrum of p53 and Ki-ras in 67 unselected cases by direct DNA sequencing. Interestingly, insertion/deletion mutations in p53 from colorectal carcinoma in Hong Kong showed a significantly higher frequency (17.2%) than the Scottish data (0%) and the world database (6.6%), although the overall frequency of p53 mutation (43%) in Hong Kong was similar to others. The high incidence of colorectal carcinoma in young people and the raised proportion of frameshift mutations in p53 encourage further search for a genetic basis for susceptibility to this disease in the Hong Kong Chinese population.

Adolescent↗
PubMed1997

Clinicopathological pattern of pulmonary thromboembolism in Chinese autopsy patients: comparison with Caucasian series.

The clinicopathological data of adult Chinese patients identified to have 'significant pulmonary thromboembolism (PTE)' at autopsy in Queen Mary Hospital (QMH) Hong Kong, from 1990 to 1994 inclusive, were analysed retrospectively. The prevalence of PTE was documented and data were compared with published series of Caucasian patients. The parameters studied included sex-age distribution, associated diseases, symptomatology, site of venous thrombosis, duration of admission and intervals between surgery and death. The rate of PTE was 4.7% (4.5% in males and 5.2% in females). The mean age of PTE patients was significantly higher than that of non-PTE patients (p < 0.001). Two clinicopathological features worthy of note are: (1) as in Caucasian patients, most Chinese patients with 'significant PTE' do not present with leg symptoms although many of them are found to have deep vein thrombosis (DVT) at postmortem; and (2) DVT in these patients is found in the calf veins rather than in the more proximal deep veins. The recently identified racial differences in hemostasis that may contribute to the differences between Chinese and Caucasian people are discussed.

Adolescent↗
PubMed1997

Expression of vascular endothelial growth factor and its receptors in pilocytic astrocytoma.

Vascular endothelial growth factor (VEGF), a potent angiogenic and vascular permeability factor, is important in the angiogenesis of glioblastoma. A major difference between pilocytic astrocytoma, a grade I tumor, and the grade II fibrillary astrocytoma is the vascular proliferation, highly vascularized stroma, and great propensity for cyst formation in the former. In order to explore factors regulating such angiogenesis and cyst formation in pilocytic astrocytoma, we examined expression of VEGF and its receptors (KDR and Flt-1) using in situ hybridization. In all 14 cases a high level of VEGF transcripts could be demonstrated. These were found in specific regions, namely, in the tumor cyst wall, in areas of hyaline cystic degeneration, in stellate reticulated astrocytes around microcysts in the biphasic compact and loose areas, and in tumor cells with degenerative pleomorphic multicoated nuclei. KDR and Flt-1 were expressed in the tumor vasculature, with particularly high levels seen in coiled young proliferating vessels, especially those in the cyst wall. Given the known angiogenic and vascular permeability activities of VEGF, we propose that VEGF plays an important role in molding the characteristic morphologic features of this tumor, namely, the formation of cysts, microcystic pattern, hyaline cystic degeneration, hyaline vessels, and vascular proliferation. Mechanisms that block the VEGF pathway could constitute a potential therapeutic strategy for the treatment of this tumor.

Adolescent↗
PubMed1997

Persistence of hepatic hepatitis B virus after serological clearance of HBsAg with autologous peripheral stem cell transplantation.

Delayed clearance of hepatitis B surface antigen was previously reported in a 38 year old woman after high dose chemotherapy with autologous peripheral blood stem cell rescue. Sixteen months later, this patient remained hepatitis B surface antigen negative, hepatitis B surface antibody positive, and serum hepatitis B DNA negative by polymerase chain reaction. Serial liver biopsies (one at hepatitis B e antigen positive stage, one at hepatitis B e antibody positive stage, and one at hepatitis B surface antigen negative and hepatitis B surface antibody positive stage) showed a gradual resolution of the inflammatory activity with loss of hepatitis B e antigen and then hepatitis B surface antigen in the serum. However, the degree of fibrosis, though mild, remained the same. With the serological clearance of hepatitis B surface antigen, a small amount of hepatitis B virus DNA was still detectable in the nuclei of liver cells.

Adult↗
PubMed1997

Changes in hepatic portal resistance and in liver morphology during regeneration: in vitro study in rats.

OBJECTIVE: To study the effects of liver regeneration on hepatic portal resistance and on the morphology of liver sinusoids. DESIGN: Experimental in vitro study. SETTING: University laboratory, Hong Kong. ANIMALS: 10 Groups of 6 male Sprague Dawley rats each. INTERVENTIONS: Two thirds hepatectomy, with subsequent re-hepatectomy for measurements 0, 1, 3, 7, 21 and 56 days later. Perfusion of isolated livers and histomorphometry. MAIN OUTCOME MEASURES: Hepatic portal resistance and measurement of width and length of sinusoids. RESULTS: Liver weight was restored within 7 days of hepatectomy. Hepatic portal resistance/g of liver increased, reaching a maximum at 3 and 7 days of hepatectomy, and subsequently returned to initial values after 56 days. Width of sinusoids decreased to a minimum within 3 to 7 days of hepatectomy, and subsequently returned close to initial values within 56 days of hepatectomy. The changes in hepatic portal resistance occurred in phase with the changes in the width of liver sinusoids. CONCLUSIONS: There is a transient increase in hepatic portal resistance/g of liver during regeneration; transient narrowing of sinusoids may contribute to this change.

Animals↗
PubMed1996

An Epstein-Barr virus positive undifferentiated carcinoma in the lacrimal sac.

We report a Chinese patient who presented with metastatic undifferentiated carcinoma in the cervical lymph node of unknown primary origin. Despite a raised IgA titre against Epstein-Barr virus capsid antigen, examination and biopsy of the nasopharynx were negative. Radiotherapy was given to the head and neck region with the orbit shielded. There was complete resolution of the metastatic lymph nodes. She developed proptosis of her left eye one year afterward when a large tumour was found in the lacrimal sac region. Review of the initial computerized tomography revealed a small soft tissue mass in the same region. The tumour was composed of undifferentiated carcinoma cells associated with dense lymphoid infiltrate. In situ hybridization for Epstein-Barr virus EBER RNA showed strong positive signals in the malignant cells. This is the first reported case of an Epstein-Barr virus positive undifferentiated carcinoma with lymphoid stroma in the lacrimal sac. In addition to the nasopharynx, salivary glands, nasal cavity and paranasal sinuses, the lacrimal sac should be considered as a potential primary site for Epstein-Barr virus positive metastatic undifferentiated carcinoma in the cervical lymph nodes.

Adult↗
PubMed1996

Germ cell tumour as a diagnostic pitfall of metastatic carcinoma.

AIM: Testicular germ cell tumours may present as metastases in cervical lymph nodes, yet the primary tumours remain clinically occult. The aim of the study is to alert pathologists and clinicians to this uncommon but important presentation and highlight the clues and the diagnostic adjuncts to its correct diagnosis. METHODS: The clinical, cytological, histological, and immunohistochemical features of two patients with germ cell tumour initially presenting as cervical lymphadenopathy were described and analysed. RESULTS: Both patients were young adult males, who were found to have metastatic undifferentiated carcinoma on fine needle aspiration of the enlarged cervical lymph nodes. The tumour cells in both cases were positive for placental alkaline phosphatase (PLAP) and negative for epithelial membrane antigen (EMA). CONCLUSIONS: Clinicians and pathologists should be aware of the possibility of germ cell tumour when encountering a young adult male with metastatic poorly differentiated carcinoma. Positivity for PLAP and negativity for EMA are helpful adjuncts in arriving at the correct diagnosis.

Adult↗
PubMed1996

Long-term survival after gastrectomy for advanced bleeding or perforated gastric carcinoma.

OBJECTIVE: To find out whether massive bleeding or free perforation of advanced gastric carcinoma affect long term survival after gastrectomy. DESIGN: Retrospective analysis of prospectively collected data. SETTING: Teaching hospital, Hong Kong. INTERVENTIONS: Gastrectomy. MAIN OUTCOME MEASURES: Long term survival. RESULTS: Data of 50 patients with gastric carcinoma that had penetrated the serosa (pT3) and who were operated on between 1985 and 1990 were analysed. A total of 17 patients with tumour free perforation and 10 with massive bleeding underwent emergency gastrectomy, and 23 patients with comparable uncomplicated tumours had elective gastrectomy. Twelve variables that could have influenced survival including malignant perforation, bleeding, or the absence of complications were analysed using the Cox's proportional hazards model. Survival was influenced only by proliferative cell nuclear antigen (PCNA) index and not by perforation, bleeding, or the uncomplicated nature of the tumour. CONCLUSIONS: These findings suggest that perforation or bleeding from advanced gastric carcinomas do not significantly affect long term survival after gastrectomy.

Aged↗
PubMed1995

In situ detection of Epstein-Barr virus in non-small cell lung carcinomas.

Epstein-Barr virus (EBV) is strongly associated with nasopharyngeal carcinoma and lymphoepithelioma-like carcinomas (LELC) of foregut-derived organs. Recently this group of EBV-associated carcinomas has been expanded by the identification of the virus in conventional adenocarcinomas of the stomach. In situ hybridization (ISH) using a sensitive digoxigenin-labelled EBER RNA probe was performed on 167 consecutive unselected primary non-small cell lung carcinomas, to determine the frequency of EBV association in these tumours. Nine cases (5.4 per cent) showed strong EBER signals in the tumour cell nuclei. By immunohistochemistry, four of the EBER-positive tumours showed patchy expression of the viral latent membrane protein (LMP-1) and none showed any expression of the EBV nuclear antigen 2 (EBNA2). Morphologically, all the positive tumours were LELC, whereas no conventional type of non-small cell lung carcinoma showed EBV association. The LELC presented a morphological spectrum from undifferentiated to squamoid or glandular differentiation. The patients showed a male to female ratio of 8:1. The mean age at presentation was 48 years. Smoking was not a risk factor. All patients were alive at follow-up periods of 23-52 months. Southern blot analysis performed on eight of the nine positive tumours showed a clonal episomal form of EBV, suggesting the clonal expansion of an infected tumour cell early in oncogenesis. These characteristics of the EBV-associated lung tumours justify their consideration as a distinct clinicopathological entity.

Adult↗
PubMed1995

Epstein-Barr virus is present in a wide histological spectrum of sinonasal carcinomas.

Nasopharyngeal carcinomas, a common occurrence in Southern Chinese people, shows a strong association with Epstein-Barr virus (EBV); in the same population, sinonasal carcinomas are distinctly rare. Although most nasopharyngeal carcinomas are lymphoepitheliomas, sinonasal carcinomas have a wide morphological spectrum. We studied the clinicopathological features and EBV status of 29 sinonasal carcinomas from Hong Kong Chinese patients. By in situ hybridization using antisense Epstein-Barr virus early RNA (EBER) probe, seven tumors were shown to be strongly positive for the EBV RNA. They displayed a wide morphological spectrum, including one cylindric cell carcinoma, one intestinal type adenocarcinoma, four nonkeratinizing squamous cell carcinomas, and one undifferentiated carcinoma. All were from elderly subjects (mean age, 67), including six men and one woman. Three of these seven patients had complete remission after radiotherapy with a median follow-up period of 29 months. In two cases, EBV latent membrane protein-1 was expressed. Detection of the virus in a number of histological subtypes, including cylindric cell carcinoma and adenocarcinoma, suggests that EBV may play a role in the pathogenesis of a diverse spectrum of carcinomas.

Aged↗
PubMed1995

The effect of nicotine and its interaction with carbon tetrachloride in the rat liver.

In order to study the effects of nicotine on liver, groups of rats were given nicotine doses that simulated those seen in chronic smoking (54 and 108 mumol/l of nicotine) for 10 days. A subgroup was also given a single subcutaneous injection of 6 g/kg of carbon tetrachloride (CCl4) shortly before the animals of the group were killed. Histology demonstrated a significant hepatotoxic effect in the group receiving 108 mumol/l of nicotine when compared with the control group in the form of fatty change, focal or confluent necrosis and dark-cell change. The effects in pregnant rats were less severe. Carbon tetrachloride alone induced significant fatty change and focal necrosis in non-pregnant rats but not in pregnant rats. Nicotine also aggravated the CCl4 induced pathological changes in livers of both non-pregnant and pregnant animals. Thus nicotine alone, when given at a concentration of 108 mumol/l, exerted hepatotoxic effects; the alkaloid also aggravated the hepatotoxicity of CCl4. Pregnant rats were more resistant to the hepatotoxic effects produced by nicotine and CCl4.

Animals↗
PubMed1995

Lymphoepithelial carcinoma of the salivary gland: in situ detection of Epstein-Barr virus.

AIM: To examine the role of Epstein-Barr virus (EBV) in lymphoepithelial carcinoma of the salivary gland in Hong Kong Chinese. METHODS: Ten cases of lymphoepithelial carcinoma of the salivary gland (eight parotid and two submandibular) were examined. In situ hybridisation was used to localise EBER RNA, immunohistochemical methods to detect expression of latent membrane protein 1 (LMP-1) in EBV positive tumours, and Southern blot analysis to examine the clonality of EBV in the two cases where frozen tissue was available. RESULTS: None of the cases had a history of Sjögren's syndrome or histological evidence of a benign lymphoepithelial lesion. The IgA antibody titre against EBV viral capsid antigen was elevated in four cases. All cases were EBV positive by in situ hybridisation, with a strong uniform positive signal in the epithelial cells, and all cases expressed LMP-1. Southern blot analysis revealed that the clonal episomal form of the virus was present. Two of the three female patients in this series also developed carcinoma of cervix. One of these carcinomas had histological features of a lymphoepithelioma-like carcinoma but was EBV negative. CONCLUSIONS: A consistent association between EBV and lymphoepithelial carcinoma of the salivary gland was found. The presence of the virus in a clonal episomal form, and the expression of LMP-1 viral oncoprotein is further evidence of the role of EBV in the oncogenesis of this tumour.

Adult↗
PubMed1995

Seasonal variation in the necropsy incidence of pulmonary thromboembolism in Hong Kong.

The seasonal variation in the necropsy incidence of significant pulmonary thromboembolism in Hong Kong was investigated. A total of 3446 adult Chinese necropsies carried out in Queen Mary Hospital, Hong Kong, from 1987 to 1992 showed an overall rate of 3.77% for significant pulmonary thromboembolism. The rates for individual months were calculated and compared. The pattern of seasonal variation showed that there are two troughs in early summer (June, July) and early winter (November, December), with rates between 1.6% and 2.4%. The rates in the months for the rest of the year were between 4.0% and 5.5%. The overall pattern was similar to that of the temperate zone although the climate was quite different.

Adolescent↗
PubMed1994

Fine-needle aspiration biopsy of pilomatrixoma: still a diagnostic trap for the unwary.

Of the 16 cases of fine-needle aspiration biopsy (FNAB) of pilomatrixomas reported since 1982, only 25% were correctly diagnosed prior to excision. The most common pitfall encountered was a false-positive or suspicious diagnosis of a carcinoma. All the reported cases had a polymorphous cellular and noncellular composition on low-power examination, including numerous basaloid cells, ghost cells, squamoid cells, foreign body giant cells, mixed inflammatory cells, keratin clumps, and granular debris which might be easily mistaken for a malignant necrotic background. Amongst these, ghost cells were the critical pathognomonic feature. This paper reported a further finding that had been underemphasized in the literature: masses of refractile orangeophilic keratin clumps representing compact sheets and stacks of ghost cells. Their presence should alert the observer to search for the more diagnostic dispersed forms which otherwise might be inconspicuous and easily overlooked.

Adult↗
PubMed1994

In situ detection of Epstein-Barr virus in gastric and colorectal adenocarcinomas.

The association of Epstein-Barr virus (EBV) with lymphoepithelioma-like carcinoma in the nasopharynx, which is common in Chinese from the southern region, is well established. Recently, EBV has also been found to be associated with lymphoepithelioma-like carcinomas (LELCs) and carcinomas with prominent lymphoid infiltrates in the stomach. We investigated for the presence of EBV in 74 cases of gastric adenocarcinoma and 36 cases of colorectal adenocarcinoma from Chinese patients by in situ hybridization (ISH) using an antisense EBER probe. In seven cases (9.5%) of gastric carcinoma, EBER was highly expressed in the adenocarcinoma cells and metastatic tumor cells in regional lymph nodes. In all these cases, the normal gastric epithelium was EBV negative. None of the colorectal carcinomas showed a positive signal. Isolated positive lymphoid cells were frequently found in both tumors. Of the seven positive cases, only one was LELC, and the others were conventional adenocarcinomas of the intestinal type. Five showed expression of the viral RNA in all tumor cells as well as the surrounding dysplastic epithelium. Interestingly, the sixth case showed distinct negative islands of dysplastic glands adjacent to strongly positive dysplastic glands and invasive carcinoma cells. This pattern of positivity, together with negative normal gastric epithelium and positive metastatic tumor, suggested that EBV infection occurred in the dysplastic phase and that an apparent growth advantage was conferred by the EBV infection.

Adenocarcinoma↗