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Biomedical subjects

Y F Chung

Publications and source records attributed to Y F Chung.

17 recordsLinked to original sources
PubMed2003

Breath-hold fast recovery fast spin echo versus conventional non-breath-hold fast spin echo T2-weighted MR imaging of focal liver lesions.

INTRODUCTION: We compare the breath-hold fast recovery fast spin echo (BHFRFSE) T2-weighted and non-breath-hold fast spin echo (NBHFSE) T2-weighted sequences in image quality and lesion characterisation of focal liver lesions. MATERIALS AND METHODS: Fat-suppressed T2-weighted magnetic resonance (MR) images obtained with the 2 sequences (BHFRFSE and NBHFSE) in 79 patients with 113 liver lesions were analysed retrospectively. The image quality and nature of the lesions were evaluated by 2 experienced radiologists. RESULTS: Based on receiver operating characteristic curve analysis, lesion characterisation was comparable for both sequences. The image quality of BHFRFSE was significantly better than that of NBHFSE. The NBHFSE missed 4 malignant lesions while BHFRFSE missed 2 malignant lesions. CONCLUSION: BHFRFSE performs similarly to NBHFSE in image quality and liver lesion characterisation.

Adult↗
PubMed2003

Clinical applications of MR cholangiopancreatography.

INTRODUCTION: We review the clinical applications of magnetic resonance cholangiopancreatography (MRCP) and illustrate them with clinical examples. METHODS: A literature search was performed in MedLine using the keywords "MR cholangiopancreatography" and "MRCP". The relevant articles were reviewed. The radiology information system was searched for MRCP examinations performed from July 1999 to December 2002. A surgical database of resected cases was also referenced. Illustrative cases were chosen in consultation with surgical authors to show the clinical applications of MRCP. RESULTS: MRCP is useful for assessment of choledocholithiasis, choledochal cysts, pancreas divisum, primary sclerosing cholangitis, pancreatitis and anatomical variation of the biliary ducts. When complemented with dynamic gadolinium-enhanced studies, MRCP is useful for assessment of ductal cholangiocarcinoma, pancreatic and gall bladder neoplasms. Illustrative cases are provided. CONCLUSION: MRCP is an important modality for the clinical assessment of biliary and pancreatic disorders.

Bile Duct Neoplasms↗
PubMed2001

Recurrent chromosomal rearrangements involving breakpoints 3p21 and 19q13 in Chinese IgD multiple myeloma detected by G-banding and multicolor spectral karyotyping: a review of IgD karyotype literature.

Immunoglobulin D multiple myeloma (IgD MM) is a rare subtype that accounts for 1% to 3% of MM and shows higher aggressiveness with distinctive clinical and laboratory features. However, there is little information in the literature on their karyotypes, which are mainly derived from G-banding results. Our current study on 2 Chinese IgD MM thus represents the first description of cytogenetic data on this subtype based on an integrated analysis with G-banding and multicolor spectral karyotyping (SKY). Both of our cases showed some usual features of MM, as well as a few novel translocations including t(3;22), t(6;19), t(X;19) and the 3 whole-arm translocations namely t(1;6)(q10;p10), t(4;9)(q10;p10), and t(16;18)(q10;q10). We also identified recurrent chromosomal rearrangements involving breakpoints 3p21 and 19q13, which may suggest to be unique aberrations that may underline the pathogenesis of this distinctive biological MM subtype.

Aged↗
PubMed2000

Diagnostic failures in endoscopy for acute upper gastrointestinal haemorrhage.

BACKGROUND: Oesophagogastroduodenoscopy (OGD) is the diagnostic tool of choice in acute upper gastrointestinal haemorrhage. However, the factors causing diagnostic failure are not well documented or discussed. METHODS: OGDs performed by a single surgeon for acute upper gastrointestinal haemorrhage were reviewed retrospectively for 'missed' diagnosis. RESULTS: There were nine cases (1.4 per cent) of 'missed' diagnosis in 638 OGDs performed over a 3-year period. Incomplete examination caused by a fundal pool precluded three examinations in which two Dieulafoy's lesions and one chronic gastric ulcer were later found. Other difficult examination sites were the cardia/high lesser curve (three cases), the stomal line of a gastrojejunostomy anastomosis (two) and at the junction of the first and second part of the duodenum (one). Four of the overlooked diagnoses were Dieulafoy's lesions. CONCLUSION: OGD was able to diagnose the cause of bleeding in 98.6 per cent of patients with acute upper gastrointestinal haemorrhage. The factors that caused diagnostic failure were a difficult examination site and failure to recognize lesions (Dieulafoy's).

Diagnostic Errors↗
PubMed2000

Management of intraparotid facial nerve schwannomas.

BACKGROUND: The purpose of the present paper was to review the management of intraparotid facial nerve schwannoma so as to discuss its clinical presentation, evaluate the various possible diagnostic investigations, and compare the various surgical options and outcome. METHODS: Case series was undertaken of five (1.3%) patients with facial nerve schwannoma out of 400 consecutive parotidectomies at Singapore General Hospital. RESULTS: There were three men and two women with an age range of 29-65 years. Three patients presented with painless parotid lumps while two had painful parotid swellings. None had facial nerve paresis. Only one patient had preoperative diagnosis suspicious of schwannoma by fine-needle aspiration cytology (FNAC). Diagnoses were made intraoperatively. Four patients had excision with cable grafting of the nerve defect. achieving facial nerve grade II-IV (House-Brackmann scale). One patient who underwent enucleation of tumour with nerve preservation achieved grade II. CONCLUSIONS: Preoperative diagnosis is difficult but it is important for discussion of the extent and options of surgery. Fine-needle aspiration cytology holds promise in making a preoperative diagnosis. Enucleation with nerve preservation where possible seems to offer better facial function whereas nerve excision with cable graft can give satisfactory results.

Adult↗
PubMed2000

Microdochectomy for single-duct nipple discharge.

INTRODUCTION: Isolated single-duct nipple discharge is worrying and poses a surgical dilemma. Factors predicting malignancy are controversial. MATERIALS AND METHODS: Retrospective review of 92 consecutive microdochectomies for single-duct nipple discharge in a tertiary referral centre over 8 years. RESULTS: The commonest causes were ductal papilloma (52%) and fibrocystic diseases of the breast (21%). Five (5%) patients had breast carcinoma, of whom only 1 had an invasive component. The median age of these patients was 43 years (range 26 to 72 years) which was similar to median age of the whole cohort. Sixty-seven (73%) patients presented with blood-stained nipple discharge. The 5 patients with breast carcinoma had blood-stained discharge. Mammography was abnormal in 1 out of 4 patients in the carcinoma group. CONCLUSIONS: The incidence of breast carcinoma in patients presenting with isolated single-duct nipple discharge was low (5%) among Singaporean women. There was no reliable predictors of malignancy, though all patients with carcinoma presented with blood-stained discharge. Microdochectomy still remains an effective treatment for nipple discharge both for cure and diagnosis.

Adolescent↗
PubMed1999

Combined morphological and interphase fluorescence in situ hybridization study in multiple myeloma of Chinese patients.

To gain insight into the real incidence of the numeric chromosomal aberrations and the cell lineage involvement of the neoplastic process in multiple myeloma (MM), we examined 18 Chinese MM patients by May-Grunwald-Giemsa (MGG) staining and fluorescence in situ hybridization using three DNA centromeric probes specific for chromosomes 3, 7, and 9. In this investigation, cytogenetic abnormalities were detected in plasma cells (PCs), myeloid cells (MCs), and lymphoid cells (LCs) in all of the MM patients studied. This is the first demonstration of the cytogenetic aberration involved in the myeloid series. Furthermore, the MCs and PCs of 16 MM patients had the same aneuploidies in one or more of the chromosomes analyzed. These data suggest that the neoplastic transformation of MM may occur early in the hematopoietic development. Chromosomal aberrations involving mainly subclones and considerable cellular heterogeneity with gain of a variety of copy numbers of the same chromosome were demonstrated within PCs, which may possibly be the result of an underlying defect of PCs in the control of their number of chromosomes. Whereas PCs showed evidence suggestive of increased polyploidization, MCs and LCs, which exhibited similar chromosomal patterns as the former, rarely did. Thus, the clonal evolution from LC to PC, if that happens in MM, is characterized by chromosomal instability favoring growth of tumor cells with polysomies and polyploidies.

Adult↗
PubMed1999

Minimizing recurrence after sigmoid volvulus.

BACKGROUND: This study was a retrospective review of a series of patients with sigmoid volvulus to identify risk factors for recurrence and recommend appropriate treatment. METHODS: Thirty-five patients with sigmoid volvulus were treated over 8 years. RESULTS: Six patients had emergency surgery for peritonitis. Twenty-eight of the other 29 patients had successful endoscopic decompression; 15 of these patients had elective surgery during the same admission. Twelve of the 14 patients who refused operation after endoscopic decompression developed recurrent volvulus, a median of 2.8 months later. Eight subsequently agreed to surgery and underwent elective operation following repeat decompression. Of 29 patients who had surgery, 27 had sigmoid colectomy (two were initial Hartmann procedures) and two had subtotal colectomy. Six patients who had sigmoid colectomy developed recurrent volvulus. Concomitant megacolon and megarectum at the time of initial surgery were significant predictors of recurrence. CONCLUSION: Subtotal colectomy, carried out as the primary procedure if there is concomitant megacolon or megarectum, might reduce the risk of recurrent sigmoid volvulus.

Adolescent↗
PubMed1999

Epidemiology of Warthin's tumour of the parotid gland in an Asian population.

BACKGROUND: Recent studies have documented a number of changing demographic features in the occurrence of Warthin's tumour (adenolymphoma) of the parotid gland. In order to analyse its epidemiology in an Asian population, a retrospective study was performed on all parotid neoplasms (n = 289) operated on between 1988 and 1998. PATIENTS AND METHODS: A total of 209 consecutive patients were selected for study, 136 with pleomorphic adenomas (one bilateral) and 73 with Warthin's tumours (seven bilateral). Patients were analysed with regard to tumour incidence, age, sex and race. Smoking as an aetiological factor in the development of Warthin's tumour was also studied. RESULTS: Warthin's tumour formed 25 per cent of parotid tumours and its ratio to pleomorphic adenomas was 1 : 1.9. Multicentricity was found in 14 patients (19 per cent). The male : female ratio for Warthin's tumours was 4.6 : 1. The proportion of Warthin's tumours did not show any increasing trend relative to pleomorphic adenomas. The racial distribution of Warthin's tumours showed an increased incidence among Chinese and a reduced incidence among Malays and Indians. The adjusted odds ratio for sex and age favouring an association between smoking and Warthin's tumour was 39.5 (95 per cent confidence interval 10.5-149. 0; P < 0.0001). CONCLUSION: The incidence of Warthin's tumour is considerable among Asians although there is still male predominance. There is no rising incidence of Warthin's tumour; the trend parallels the declining smoking rate in the population. The lower incidence among ethnic groups with dark skin seems to suggest concomitant genetic factors other than environmental factors alone in histogenesis. Smokers have a 40-fold greater risk than non-smokers of developing a Warthin's tumour.

Adenolymphoma↗
PubMed1999

Splenic angiosarcoma--an unusual cause of bleeding gastrointestinal tract.

Splenic angiosarcoma is a rare malignant vascular tumour with about 100 reported cases to date. The presentation of splenic angiosarcoma is highly variable, frequently causing diagnostic difficulty. It usually presents with splenomegaly, abdominal pain and occasionally with a microangiopathic type of anaemia. Here we report an additional case of primary angiosarcoma of the spleen presenting as a problem of bleeding from the gastrointestinal tract.

Gastrointestinal Hemorrhage↗
PubMed1998

Young age is not a poor prognostic marker in colorectal cancer.

BACKGROUND: There is still considerable controversy and debate regarding the features and prognosis of colorectal cancer in young patients. METHODS: One hundred and ten patients (5.1 per cent) under the age of 40 years with colorectal cancer (group Y; male: female ratio 48:62) were compared with 2064 patients with colorectal cancer aged 40 years or more (group O; 917 women, 1147 men). Mode of presentation, stage at diagnosis, tumour characteristics and survival were analysed. RESULTS: Predisposing malignant conditions and family history of colorectal cancer were present in 20.9 per cent of patients in group Y versus 2.2 per cent in group O (P < 0.001). Common chief complaints included change in bowel habits, bleeding from the rectum and a significantly higher incidence of abdominal pain in group Y. There was no difference in stage at presentation between the two groups (the proportion of Dukes stage A, B, C and 'D' lesions in group Y was 8.2, 24.5, 37.3 and 30.0 per cent respectively versus 10.5, 27.9, 33.4 and 28.1 per cent in group O). Tumour site and characteristics were similar in both groups. The incidence of mucinous/signet ring cell and poor grade tumours was 6.9 and 11.8 per cent respectively in group Y and 4.5 and 10.5 per cent in group O. With a mean follow-up of 31.8 months, the overall 5-year survival rate was 54.8 per cent in group Y and 54.1 per cent in group O. Comparing stage for stage, survival was not significantly different in the two groups. However, the adjusted hazard ratios of the age groups Y, M (40-59 years), S (60-79 years), and E (80 years and above) were 1.3, 1 (baseline for calculations), 1.4 and 2.4 respectively, suggesting an adverse outcome for patients in group Y compared with patients aged 40-59 years. CONCLUSION: This study revealed no difference in tumour characteristics and survival in patients with colorectal cancer aged less than 40 years compared with those aged above 40 years. However, a higher hazard ratio in the youngest group may connote a worse prognosis than that for those aged 40-59 years. A significant family history of colorectal cancer and predisposing conditions in the young warrants aggressive screening, surveillance and treatment of the underlying conditions. The detection of colorectal cancer in young patients should be no different from that in the old but demands a high index of suspicion.

Adult↗
PubMed1998

Management of colonic lipomas.

BACKGROUND: Little is known of colonic lipomas, especially in an Asian population, and their management is controversial. METHODS: A computerized colonoscopy database was analysed and patients with colonic lipomas were reviewed. RESULTS: There were 16 colonic lipomas (incidence of 0.15%) in a series of 10658 consecutive colonoscopies. There were seven men and nine women, with a mean age of 61.8 years (range: 28-80 years). The size of the lipomas ranged from 1.5 to 6 cm; all those larger than 3.5 cm were symptomatic (P = 0.05). The most common symptom was mild bleeding per rectum. Right-sided lipomas were palpable while left-sided lipomas presented with obstructive symptoms. Colonoscopic removal by hot biopsy or snare polypectomy was possible where the lipomas were 2.5 cm and pedunculated. Surgery was performed in six patients (four open, two laparoscopic) for symptoms and to exclude malignancy. There was no morbidity or mortality. CONCLUSIONS: Small or pedunculated lipomas may be safely removed colonoscopically and the diagnosis confirmed histologically. Larger lipomas require surgical resection for relief of symptoms or to exclude malignancy.

Adult↗
PubMed1998

Transcriptional silencing of the p16 gene in human myeloma-derived cell lines by hypermethylation.

Recently, p16 and p15 have been identified as commonly inactivated tumour suppressor genes in haematological malignancies. We previously reported that these genes were frequently hypermethylated in multiple myeloma (MM). To investigate how p16 and p15 inactivation are associated with hypermethylation, methylation status and transcription of these genes in six MM-derived cell lines were studied by Southern blot analysis and RT-PCR. Aberrant methylation of p16 was found in ARH-77, HS-Sultan, IM-9, RPMI-8226, U266-B1 and NCI-H929 MM cell lines. However, loss of p16 transcription was demonstrated only in HS-Sultan, RPMI-8226, U266-B1 and NCI-H929 with extensive methylation at the 5' upstream region of p16. Conversely, only HS-Sultan showed extensive methylation at the 5' upstream region of p15, which was associated with p15 transcriptional block. These results suggest that extensive methylation within a critical domain may be crucial in silencing p16 or p15 transcription. To demonstrate the reversibility of methylation and its relationship with transcription, HS-Sultan, RPMI-8226 and NCI-H929 were demethylated with 5-aza-2'-deoxycytidine. Restoration of gene transcription was observed and correlated with partial demethylation of the genes. The present data show that the p16 and p15 genes are silenced in MM by hypermethylation, which may play an important role in MM pathogenesis.

Blotting, Southern↗
PubMed1997

Frequent hypermethylation of p16 and p15 genes in multiple myeloma.

Both p16 and p15, encoded by the genes located on chromosome 9p21, are inhibitors of cyclin-dependent kinases (CDK4/6) and the upstream regulators of Rb function. In hematopoietic malignancies, deletion of p16/p15 locus has been shown to be highly specific to lymphoid, and more particularly from B-lineage malignancies except multiple myeloma (MM). To investigate whether these genes are inactivated by deletions, mutations, and hypermethylation of the 5' CpG islands, we examined 12 MM patients by Southern hybridization and polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analysis. No deletions nor mutations of the p16 and p15 genes were found. However, hypermethylation was observed in 75% for p16 and 67% for p15 in our group of MM patients. Such high frequencies of involvement of these genes in MM make them hitherto the most common genetic abnormalities in this disease. Concomitant hypermethylation, uncommon thus far in the literature of the study of these genes, is a rather common phenomenon, occurring in 67% of our patient group. Moreover, hypermethylation of p16/p15 was associated with blastic disease and concomitant hypermethylation of both genes may be pathogenetically related to plasmacytoma development. These results indicate that these genes are important in MM pathogenesis. Here we report, for the first time in the literature, the high incidences of p16 and p15 alterations in MM, not by homozygous deletions or mutations, but solely by hypermethylation of the 5' CpG islands, which may be a specific mechanism in this disease.

Adult↗
PubMed1997

Pediatric nosocomial fungal infections.

During a period of twelve years (1984-1995), ninety-seven pediatric patients experienced 107 nosocomial fungal infections at Mackay Memorial Hospital. The nosocomial fungal infection rate in pediatric patients was lower than that of the hospital as whole, but it increased significantly. The average rate in the last three years (1993-1995) was 1.20 per thousand discharged patients, 10 times that of the first three years (1984-1986). Two-thirds of the patients were below one year of age. Half of the infections occurred in Intensive Care Units. The bloodstream was the most common site of infection (40.2%), followed by the urinary tract and skin. Important underlying diseases included malignancies, prematurity, and congenital anomalies. Common risk procedures included total parenteral nutrition (43.3%), endotracheal intubation (29.9%), central venous catheterization (25.8%), operation (14.4%). Near 90% of the patients had previously received antibiotics. Candida albicans was responsible for 58.1% of the infections. Thirty-three patients expired, of whom 18 died of the fungal infections. With the trend of increasing nosocomial fungal infections, physicians should be more alert to the possibility of such infections.

Adolescent↗
PubMed1996

Hypermethylation of the p16 gene in nasopharyngeal carcinoma.

We have recently reported that inactivation of the p16 gene by mutation and deletion is common in nasopharyngeal carcinoma (NPC). The present study demonstrates that hypermethylation of the 5' CpG island can serve as an alternative mechanism for inactivation of the p16 gene in this tumor. Using Southern blotting analysis and multiplex PCR, aberrant methylation of the 5' CpG island of the p16 gene was found in a NPC xenograft (xeno-666) and 6 (22%) of 27 primary tumors, but not in normal tissues of the nasopharynx. In the NPC xenograft (xeno-666) and its newly derived cell line (cell-666), both showing hypermethylation of the p16 gene, no p16 gene expression was found. After treatment with 5-aza-2'-deoxycytidine, reexpression of the p16 gene was detected in the cell line cell-666. These findings suggest that aberrant methylation of the 5' CpG island may participate in the transcriptional inactivation of the p16 gene in NPC. The present results further support that the p16 gene is the critical target on chromosome 9p21 for inactivation during the development of this disease.

Carrier Proteins↗