Biomedical subjects

J K Chan

Publications and source records attributed to J K Chan.

At least 73 records · Page 4Linked to original sources

PubMed1999

Applicability of living donor liver transplantation to high-urgency patients.

BACKGROUND: Cadaveric liver donors are scarce in Hong Kong, and the application of liver transplantation to high-urgency patients is limited. We evaluated the use of grafts from living donors in this setting. METHODS: From July 1994 to January 1998, 49 consecutive adult patients who were intensive care unit-bound because of acute or chronic liver failure were put on a high-urgency list for liver transplantation. Family members were not solicited for living donation, and the initiation and decision for living donor liver transplantation (LDLT) was based on the donor's voluntary intent. Assessment of the living donor, including blood tests, computed tomographic volumetry, and angiography, was performed only after informed consent was executed. RESULTS: In 25 of 49 (51%) patients, no family member volunteered as living donor; 23 died awaiting donor organs, and 2 received a cadaveric graft. Twenty-four (49%) patients had 36 family members who volunteered as living donors. Before evaluation of living donor was completed, two patients received a cadaveric liver transplant. LDLT was not performed in nine patients because of recipient contraindications (n=4), ABO blood group incompatibility (n=3), and withdrawal of donor (n=2). Eight of these nine patients died, and one received a cadaveric liver graft. The remaining 13 (27%) patients received grafts from living donors. Four of 5 (80%) patients who underwent cadaveric liver transplantation and 11 of 13 (85%) who underwent LDLT survived. Thus, emergency transplantation from living donors increased the applicability of liver transplantation from 10% to 37%, and the survival rate after emergency LDLT (85%) was superior to that of the remaining patients (11%). CONCLUSIONS: When cadaveric organ donation is scarce, emergency liver transplantation from living donors can be applied to high-urgency adult patients.

Adolescent↗

PubMed1999

Linker for activation of T cells (LAT), a novel immunohistochemical marker for T cells, NK cells, mast cells, and megakaryocytes: evaluation in normal and pathological conditions.

LAT (linker for activation of T cells) is an integral membrane protein of 36-38 kd that plays an important role in T cell activation. Using a rabbit polyclonal antibody generated against the cytosolic portion of LAT, we investigated the immunohistochemical expression of LAT in normal and pathological hematolymphoid tissues. LAT reacts with human T cells in paraffin sections, including decalcified bone marrow trephines. LAT appears early in T cells at the thymocyte stage and before TdT expression in embryos, and is expressed in peripheral lymphoid tissues, without restriction to any T cell subpopulations. In addition to T cells, natural killer (NK) cells (evaluated with flow cytometry), megakaryocytes and mast cells are also LAT-positive, whereas B cells and other myeloid and monocytic derived cells are negative. Tested on a total of 264 paraffin-embedded tissue biopsies, LAT reacted with the great majority (96.8%) of T/NK-cell neoplasms, covering the full range of T cell maturation. Although antibodies to both LAT and CD3 had a similarly high sensitivity in the staining of T/NK-cell lymphomas, when used in conjunction, they successfully identified a higher number of cases (98.4%). Atypical megakaryocytes from different hematological disorders, as well as mast cells in mastocytosis were also LAT-positive, but all neoplasms of B cell origin, Hodgkin's lymphomas, and several nonlymphoid malignancies were negative. These data indicate that the anti-LAT antibody may be of value to diagnostic histopathologists for the identification of T cell neoplasms.

Adaptor Proteins, Signal Transducing↗

PubMed1999

Comparative genomic hybridization analysis of natural killer cell lymphoma/leukemia. Recognition of consistent patterns of genetic alterations.

Putative natural killer (NK) cell lymphoma/leukemia is a rare group of recently characterized hematolymphoid malignancies. They are highly aggressive and frequently present in extranodal sites, including the nasal area and the upper aerodigestive system, and nonnasal areas such as the skin and the gastrointestinal tract. According to clinicopathological features, they can be classified into nasal NK cell lymphoma, nasal-type NK cell lymphoma occurring in nonnasal areas, and NK cell lymphoma/leukemia. Genetic alterations in NK cell lymphoma/leukemia are not well defined. In this study, we have performed comparative genomic hybridization (CGH) on DNA extracted from fresh or frozen tissues of 10 patients with NK cell lymphoma/leukemia. They comprised four nasal NK cell lymphomas, one nasal-type NK cell lymphoma, and five NK cell lymphomas/leukemias. CGH showed frequent deletions at 6q16-q27 (four cases), 13q14-q34 (three cases), 11q22-q25 (two cases), 17p13 (two cases), and loss of the whole chromosome X (two cases). DNA amplification was observed in a majority of the chromosomes. Five cases showed DNA gains at region 1p32-pter. Frequent DNA gains were also found in chromosomes 6p, 11q, 12q, 17q, 19p, 20q, and Xp (three cases each). Interestingly, DNA gains were more frequent in nasal/nasal-type NK cell lymphomas than NK cell lymphoma/leukemia. These genetic alterations correlated well with karyotypic features found in some of the cases. The frequent DNA losses at 6q and 13q suggest that the presence of tumor suppressor genes at these regions is important in NK cell transformation. In addition to establishing novel patterns of genomic imbalances in these rare NK cell malignancies, which may be targets for future molecular analysis, this study also provides important information on genetic alterations in NK cell lymphomas that may be useful in defining their positions in current lymphoma classification schemes, which are increasingly focusing on phenotypic and genotypic correlations.

Adolescent↗

PubMed1999

Liver transplantation in infants.

PURPOSE: In view of the earlier reports that children below 1 year of age constitute a high-risk group for liver transplantation, the authors reviewed their experience in performing orthotopic liver transplantation in this age group. METHODS: The records of 9 children aged less than 1 year who underwent 6 living-related liver transplants and 3 reduced-size liver transplants between December 1993 and June 1997 were reviewed. RESULTS: Five reexplorations were required for 3 children who had 1 or more of the following early complications: bleeding from hepatic vein to inferior vena cava anastomosis (n = 1), right hepatic vein stump bleeding (n = 1), intraabdominal hematoma (n = 2), jejuno-jejunostomy leakage (n = 1), and colonic perforation (n = 1). Late complications include stricture at the biliary-enteric anastomosis requiring percutaneous balloon dilatation (n = 3) and hepatitis of undetermined etiology requiring retransplantation (n = 1). There was no hepatic artery thrombosis despite the small arteries available for anastomosis. Follow-up ranged from 19 to 61 months (mean, 40 months). Patient survival rate was 100%, and graft survival with good liver function was 89%. All living donors, 2 fathers and 4 mothers, are well. CONCLUSIONS: Liver transplantation in infants less than 1 year of age is technically demanding but feasible and still can be performed with a good outcome. Age alone (under 1 year) should not be considered as a contraindication for liver transplantation.

Age Factors↗

PubMed1999

Peripheral T and putative natural killer cell lymphomas commonly coexpress CD95 and CD95 ligand.

The CD95 (Fas)/CD95 ligand (CD95L) system is an important mechanism triggering apoptosis, and CD95L expression has recently been implicated for immune evasion and aggressive behavior in malignancies. This study aimed to investigate CD95 and CD95L expression in lymphomas and the possible relationship with tumor cell apoptosis, with emphasis on the natural killer (NK) cell lymphomas, which are highly aggressive neoplasms and frequently exhibit tumor cell apoptosis/necrosis. Frozen sections of 82 cases of lymphomas obtained from Queen Elizabeth Hospital and Caritas Medical Center, Hong Kong, were immunostained with polyclonal anti-CD95 and anti-CD95L antibodies. The NK-cell lymphomas were also studied for apoptosis by in situ end labeling (ISEL) method, and zonal tumor cell death was evaluated semiquantitatively. The cases studied included 27 NK-, 22 T-, and 33 B-cell lymphomas. CD95 was expressed in 25 (93%) NK-, 11 (50%) T-, and 14 (42%) B-cell lymphomas. CD95L was expressed in 19 (70%) NK-, 15 (68%) T-, and 3 (9%) B-cell lymphomas. There was significant difference in the frequency of CD95 expression between B- and NK- (P < .001), and between T- and NK-cell lymphomas (P < .05), and in CD95L expression between B- and T- (P < .01) or NK-cell (P < .01) lymphomas. Zonal tumor cell death was present in 21 (78%) NK-cell lymphomas and 1 (4.5%) T-cell lymphoma and showed no correlation with CD95 or CD95L expression. ISEL analysis showed apoptosis predominantly in the viable areas in only 5 (24%) NK-cell lymphomas. In conclusion, CD95L is frequently expressed in NK- and T-cell lymphomas, but rarely in B-cell lymphomas. Zonal tumor cell death is not correlated with CD95 or CD95L expression and thus the CD95/CD95L system probably does not contribute significantly to this phenomenon. We postulate that the frequent expression of CD95L by NK- and T-cell lymphomas may mediate local or systemic tissue damage and immune evasion, and may contribute to the clinical aggressiveness of these tumors.

Apoptosis↗

PubMed1999

Cytogenetic abnormalities in chronic B-cell lymphoproliferative disorders in Chinese patients.

We analyzed the cytogenetic findings of 59 Chinese patients with chronic B-cell lymphoproliferative disorders. More than half of the patients (n = 36, 61%) had chronic lymphocytic leukemia. Cytogenetic abnormalities were demonstrated in 44.1% (26/59) of the patients. Trisomy 12 was the most frequent abnormality in chronic lymphocytic leukemia and was found in 27.8% (10/36) of the patients, indicating that the incidence of trisomy 12 in chronic lymphocytic leukemia in Chinese patients might not be low compared with the West as previously suggested. Structural abnormalities involving chromosomes 13 at band q14 were the next most common abnormalities in patients with chronic lymphocytic leukemia. Among the 11 patients with mantle cell lymphoma in leukemic phase, t(11;14) was seen in only 2 patients (18.2%). Several unusual cytogenetic abnormalities also were found.

Adult↗

PubMed1999

T-cell prolymphocytic leukemia with a novel translocation (6;11)(q21;q23).

T-cell prolymphocytic leukemia (T-PLL) is an uncommon chronic lymphoproliferative disorder characterized by lymphadenopathy, splenomegaly, and lymphocytosis. The leukemic cells have the appearance of prolymphocytes and usually an immunophenotype of T-helper cells (CD3+ CD4+ CD8-). Inv(14q), del(11q), i(8q), and rearranged Xq28 are the commonest nonrandom chromosomal abnormalities in T-PLL. Recently, it has been shown that the ataxia-telangiectasia mutated (ATM) gene located at 11q23 is often deleted in T-PLL, suggesting a tumor suppressor role of the ATM gene on tumorigenesis of T-PLL. We report a case of T-PLL with t(6;11)(q21;q23) as the sole chromosomal abnormality and suggest that the cytogenetically identified translocation also implicates the ATM gene.

Aged↗

PubMed1999

Primary juxtaarticular soft tissue lymphoma arising in the vicinity of inflamed joints in patients with rheumatoid arthritis.

AIMS: Primary soft tissue lymphoma is uncommon and little is known regarding its aetiology and pathogenesis. In a review of 37 soft tissue lymphomas we uncovered three cases associated with rheumatoid arthritis which we report herein. METHODS AND RESULTS: The clinical records and pathology of the cases are described together with the results of in situ hybridization studies with oligonucleotide probes to Epstein-Barr virus (EBV) encoded RNA (EBER). All three patients were females with a long-standing history of rheumatoid arthritis ranging from 9 to 17 years. Each presented with a soft tissue mass in the vicinity of a joint affected by rheumatoid disease. All had received prior treatment with nonsteroidal anti-inflammatory drugs and one also received gold, penicillamine and intra-articular steroids to affected joints. None had received methotrexate. Histologically, the juxtaarticular soft tissue masses were all B-cell lymphomas. None were associated with EBV as determined by in situ hybridization. CONCLUSIONS: These cases document an association between rheumatoid arthritis and soft tissue lymphoma of B-cell type, arising in the vicinity of an affected joint. Chronic local immune stimulation may have played a significant role in the genesis of these lymphomas, unlike the frequently reversible and EBV-positive lymphomas that occur in rheumatoid patients on immunosuppressive therapy.

Adult↗

PubMed1999

Immunostaining for cyclin D1 and the diagnosis of mantle cell lymphoma: is there a reliable method?

Immunostaining for cyclin D1 has become essential for the reliable diagnosis of mantle cell lymphoma (MCL). MCL is associated with a poor prognosis and its distinction from other small B-cell lymphomas is clinically important. However, many diagnostic laboratories report problems in finding a reliable method. The following articles by Chan and by Miller, Munson & Isaacson discuss the common problems and describe successful methods with advice on diagnostic interpretation.

Cyclin D1↗

PubMed1999

Dedifferentiation in adenoid cystic carcinoma of salivary gland: an uncommon complication associated with an accelerated clinical course.

Adenoid cystic carcinoma (ACC) of the salivary gland is generally an indolent tumor that pursues a protracted clinical course with recurrences and late metastasis. The authors report three cases of ACC with dedifferentiation to high-grade malignant neoplasms. One patient developed dedifferentiated ACC ab initio, with extensive local disease and multiple lymph nodes metastases at first presentation, requiring mutilating surgery. Two patients had dedifferentiated ACC 4 and 10 years, respectively, following excision of the initial uncomplicated ACC; both patients died within 1.5 years after recurrence. Histologically, the dedifferentiated component appeared as a distinct population of anaplastic cells with more abundant cytoplasm, irregular-shaped tumor islands infiltrating a desmoplastic stroma, and total loss of bicellular differentiation characteristic of ACC. The immunophenotypic profile was altered in comparison with the ACC, such as acquisition of strong staining for S100 protein and lack of a myoepithelial component in the two cases that were interpreted as being poorly differentiated adenocarcinoma. One case was a sarcomatoid neoplasm with focal myoepithelial features. Overexpression of p53 protein was demonstrated in the dedifferentiated component in one case, and overexpression of cyclin D1 was seen in two cases. The dedifferentiated component had a higher Ki67 index than did the ACC. To the authors' best knowledge, this report represents the first documentation of dedifferentiation as a form of tumor progression in ACC, which is associated with a sinister clinical outcome.

Adult↗

PubMed1999

Mesenchymal tumors of the gastrointestinal tract: a paradise for acronyms (STUMP, GIST, GANT, and now GIPACT), implication of c-kit in genesis, and yet another of the many emerging roles of the interstitial cell of Cajal in the pathogenesis of gastrointestinal diseases?

This commentary addresses the nature of interstitial cells of Cajal (which can now be conveniently demonstrated by immunostaining for c-kit) and their possible role in the genesis of various motility disorders of the gastrointestinal tract. The evolution of the concept on the nature of gastrointestinal stromal tumors is discussed, with emphasis on the recent finding of a very high frequency of c-kit immunoreactivity in these tumors, suggesting that they might exhibit differentiation toward interstitial cells of Cajal. The practical immunohistochemical applications of antibodies to c-kit in diagnostic pathology are also discussed.

Adolescent↗

PubMed1999

Pulmonary sequestration diagnosed by contrast enhanced three-dimensional MR angiography.

Pulmonary sequestration is a congenital bronchopulmonary foregut malformation in which a segment of lung parenchyma is not connected to the tracheobronchial tree. This abnormal segment receives a blood supply from the systemic circulation. Multiple imaging modalities have been used to demonstrate the vascular anatomy of the sequestration. Different magnetic resonance angiography (MRA) techniques have been employed in the identification of these anomalous vessels. We report a case of pulmonary sequestration diagnosed by MRI with the use of contrast enhanced three-dimensional MRA.

Adult↗

PubMed1999

Prevalence of snoring and sleep-disordered breathing in a student population.

INTRODUCTION: The prevalence of snoring and sleep-disordered breathing (SDB) in young adults in Southeast Asian countries is unknown. We aim to determine the symptoms and prevalence of SDB in a university student population using a questionnaire survey followed by home sleep monitoring. METHODS: The Sleep and Health Questionnaire (a modified version of the Specialized Centers of Research Sleep Questionnaire, translated into Chinese) was distributed to all first-year students (1,306 male and 1,757 female) enrolled in the Chinese University of Hong Kong. Subsequently, those students who returned the questionnaires were randomly chosen to undergo portable home sleep monitoring using the MESAM IV device (Madaus Medizin-Elektronik; Freiburg, Germany). RESULTS: A total of 1,910 replies were obtained from 3,063 questionnaires sent by mail (response rate, 62.4%). The female to male ratio was 1.8:1, with mean age of 19.4 years (SD, 1.3 years) and mean body mass index (BMI) of 20.0 (SD, 2.5). Overall, 25.7% of subjects reported snoring; 10.7% and 42.1% reported impaired performance ability and daytime sleepiness, respectively. Of the 88 subjects who underwent overnight sleep monitoring, 66 subjects (75%) were snorers and 8 subjects (9%) snored > 10% of the night. Male subjects had a higher BMI (p < 0.001) and tended to snore more often than female subjects (p = 0.06). Subjects with an oxygen desaturation index (ODI) > or = 3 had a BMI > 22 (p < 0.05). On sleep study, nine subjects (10.2%) and two subjects (2.3%) had a respiratory disturbance index (RDI) > or = 3 and an RDI > or = 5, respectively, associated with self-reported sleepiness, giving a minimum estimated prevalence of SDB as 0.1% (RDI > or = 5) in the study population. There was no correlation between recorded snoring with either RDI or self-reported sleepiness. Questionnaire responses, neck circumference, and alcohol consumption did not predict the occurrence of SDB. CONCLUSION: Snoring was prevalent, while SDB was uncommon in this student population. However, snoring and self-reported symptoms by questionnaire were poor predictors for SDB. Male gender showed a trend as an independent predictor for snoring, but not for SDB.

Adult↗

PubMed1999

Cytogenetic abnormalities in natural killer cell lymphoma/leukaemia--is there a consistent pattern?

The group of putative natural killer cell lymphomas, also known as NK/T cell lymphomas (nasal and nasal-type) has been characterized only in recent years. Whilst a good amount of clinical information has been gathered on this group of uncommon lymphoid neoplasms, there is little information on the cytogenetic or molecular alterations. A review of the literature shows that chromosomal abnormalities are indeed commonly found in these tumours, and aberrations involving chromosome 6q are most frequent. Other non-random abnormalities include +X, i(1q), i(7q), +8, del(13q), del(17p), i(17q), and 11q23 rearrangement. It appears that deletions of the chromosome 6 at around q21-23 region is the commonest recurrent chromosomal abnormality, and fluorescence in situ hybridisation studies have confirmed the occurrence of deletions at 6q22-23 in the CD3- CD56+ tumour cells. Search for the involved genes located in this chromosome region can potentially shed light on the molecular pathogenesis of the natural killer cell neoplasms.

Chromosome Aberrations↗

PubMed1999

Peripheral T-cell and NK-cell neoplasms: an integrated approach to diagnosis.

Peripheral T-cell and NK-cell neoplasms account for only 10% of all non-Hodgkin's lymphomas, but they commonly pose great difficulties in diagnosis and classification. This article addresses the distinction between peripheral T-cell or NK-cell lymphoma and reactive lymphoid hyperplasia, the importance of recognition of the T-cell or NK-cell lineage for a lymphoma; and the importance of classification of a peripheral T- or NK-cell lymphoma. To solve these problems, it is imperative to adopt an integrated approach, taking the clinical features, morphologic findings, immunohistochemical profile, and/or genetic data into consideration.

Diagnosis, Differential↗

PubMed1999

Cribriform-morular variant of papillary carcinoma: a distinctive variant representing the sporadic counterpart of familial adenomatous polyposis-associated thyroid carcinoma?

We describe herein four cases of an unusual sporadic thyroid tumor that shares the morphologic features of a distinctive follicular cell neoplasm previously proposed as a feasible indicator of familial adenomatous polyposis. We also review five other similar cases reported in the literature. All of the nine patients were young women, aged 16 to 30 years. Grossly, the neoplasms measured 1.5 to 5.6 cm; they were solid and solitary, except one case, which showed two tumor nodules, one in each lobe. Histologically, the lesions were encapsulated, and they exhibited an intricate blending of cribriform, follicular, papillary, trabecular, and solid patterns of growth, with morular (squamoid) areas. Cribriform structures were prominent, being formed by anastomosing bars and arches of cells in the absence of intervening fibrovascular stroma. Follicular areas were usually devoid of colloid, and the papillae were lined by columnar cells. There were focal areas of trabecular arrangement reminiscent of hyalinizing trabecular adenoma. The tumor cells were cuboidal or tall, with frequent nuclear pseudostratification and abundant eosinophilic-to-oxyphilic cytoplasm. The nuclei were usually hyperchromatic, but nuclear grooves, pale or clear nuclei, and intranuclear cytoplasmic inclusions were variably present. Morules with peculiar nuclear clearing caused by biotin accumulation were scattered in the tumors. Vascular and/or capsular invasion were noted in all of the cases except one, and lymph node metastasis was found in two cases. Immunohistochemical stains showed reactivity for thyroglobulin, epithelial membrane antigen, cytokeratins (including 34betaE12), vimentin, estrogen and progesterone receptors, bcl-2, and Rb proteins. Follow-up in seven cases showed that all of the patients were alive with no evidence of disease at 1 to 13 years after diagnosis. Thus, the behavior of this variant seems to be similar to that of conventional papillary carcinoma Because of the distinctive histologic features, we propose naming this tumor the cribriform-morular variant of papillary carcinoma.

Adenomatous Polyposis Coli↗

PubMed1998

Prognostic significance of DNA flow cytometric analysis in patients with nasopharyngeal carcinoma.

BACKGROUND: Nasopharyngeal carcinoma (NPC) is a prevalent malignant tumor among Southern Chinese. Previously, the authors described the prognostic significance of a serum antibody assay to a recombinant Epstein-Barr virus Bam HI-Z replication activator protein (ZEBRA) in NPC patients with long term follow-up. In this study, the authors further reported the use of DNA flow cytometry (DNA-FCM) as an additional technique for determining the prognosis of NPC patients in the same series. METHODS: One hundred and forty-three archival biopsies from 110 NPC patients were deparaffinized and subjected to DNA-FCM analysis. DNA ploidy state and various proliferative indices (PI) of the tumors were correlated with patient survival and frequency of recurrence. RESULTS: Among the biopsies analyzed, 119 were histologically positive NPC and 24 were negative. Fifty-one tumor biopsies that fulfilled the guideline criteria of the DNA Cytometry Consensus Conference were correlated with the clinical manifestations of the patients. Among them, 43 tumors (84%) were DNA diploid and 8 (16%) were aneuploid. Two PI, S-phase fraction (SPF) and proliferation fraction (PF), appear to be potentially useful prognostic indicators. For example, PF in patients who developed locoregional recurrence (15.1%) and distant recurrence (16.4%) after radiation therapy both were significantly higher than PF in patients who were in complete remission (8.2%) (P = 0.0005 and P = 0.004, respectively). Significant differences in SPF between patients with distant recurrence (10.6%) and those in remission (5.7%) also was found (P = 0.005). Using Kaplan-Meier analysis, patients with high PF, high SPF, and aneuploid tumors had significantly poorer 12-year survival rates (35%, 26%, and 28%, respectively) than those patients with low PF, low SPF, and diploid tumors (77%, 67%, and 59%, respectively) (P < 0.0009, P < 0.004, and P < 0.01, respectively). CONCLUSIONS: Determination of tumor PI and DNA ploidy state by DNA-FCM at diagnosis of NPC can be potentially useful in selecting a poor prognostic subgroup of NPC patients. These parameters may enable oncologists to plan for more stringent treatment strategies such as hyperfractionated and accelerated radiation therapy or concomitant chemoradiotherapy for these patients.

Biopsy↗

PubMed1998

Virtual intraluminal endoscopy: a new method for evaluation and management of choledochal cyst.

A 12-year-old girl who suffered from cholangitis was treated successfully with appropriate antibiotics. She had undergone an operation in mainland China, the exact nature of which was unknown. After an ultrasound study, she underwent a helical computed tomography (CT) cholangiogram using intravenous meglumine iodoxamine. The volume data were transferred to a workstation and virtual endoscopy rendering reconstruction of bile ducts was performed. Findings of this study showed that she had cyst excision with hepaticojejunostomy (HJ), and her intrahepatic ducts were packed with stones. Virtual endoscopy gave the impression that the examiner was flying inside the lumen and showed the stricture at the HJ anastomosis, the inner surface of the bile ducts, areas of dilated intrahepatic ducts, and the intrahepatic stones. The study overcame the need for an invasive study such as a percutaneous transhepatic cholangiography (PTC) and also facilitated appropriate surgical treatment in a timely fashion. It is believed that virtual intraluminal endoscopy (VIE) is helpful in the evaluation and management of selected cases of choledochal cyst.

Anastomosis, Surgical↗