Displaying publications 1 - 20 of 158 in total

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  1. Looi LM
    Med. J. Malaysia, 2005 Jul;60 Suppl B:144-5.
    PMID: 16108199
    The liver biopsy has a unique place in the investigation of liver disease because the concepts and classification of liver disease are rooted in morphology. Today, the use of the liver biopsy has extended beyond that of diagnosis, to the assessment of disease progression, response to therapy and transplant rejection. To get the best out of the liver biopsy, it is necessary to appreciate the usefulness and limitations of the biopsy specimen. Aspects to consider include: (1) minimizing sampling errors, and appreciating that the changes in the biopsy may not be representative of the primary pathology, (2) good laboratory quality practices to avoid processing artifacts, which may render a biopsy undiagnosable, (3) the appropriate use of special stains and other laboratory techniques, (4) adoption of a systematic and algorithmic approach in the microscopic examination of the biopsy, and (5) good clinicopathological correlation.
  2. Looi LM
    Malays J Pathol, 1999 Jun;21(1):29-35.
    PMID: 10879276
    A review of routine histopathological samples and autopsies examined at the Department of Pathology, University of Malaya revealed 15 cases of amyloidosis of the lung. Two were localized depositions limited to the lung while in the remainder, lung involvement was part of the picture of systemic amyloidosis. Both cases of localized amyloidosis presented with symptomatic lung/bronchial masses and a clinical diagnosis of tumour. Histology revealed "amyloidomas" associated with heavy plasma cell and lymphocytic infiltration and the presence of multinucleated giant cells. In both cases, the amyloid deposits were immunopositive for lambda light chains and negative for kappa chains and AA protein. One was a known systemic lupus erythematosus patient with polyclonal hypergammaglobulinaemia. The other patient was found to have plasma cell dyscrasia with monoclonal IgG lambda gammopathy. Both patients did not develop systemic amyloidosis. In contrast, lung involvement in systemic AA amyloidosis was not obvious clinically or macroscopically but was histologically evident in 75% of cases subjected to autopsy. Amyloid was detected mainly in the walls of arterioles and small vessels, and along the alveolar septa. It was less frequently detected in the pleura, along the basement membrane of the bronchial epithelium and around bronchial glands. In one case of systemic AL amyloidosis associated with multiple myeloma, an "amyloidoma" occurred in the subpleural region reminiscent of localized amyloidosis. These cases pose questions on (1) whether localized "tumour-like" amyloidosis is a forme fruste of systemic AL amyloidosis and (2) the differing pattern of tissue deposition of different chemical types of amyloid fibrils, with the suggestion that light chain amyloid has a greater tendency to nodular deposition than AA amyloid.
  3. Looi LM
    Malays J Pathol, 1995 Jun;17(1):1-10.
    PMID: 8906998
    Two forms of abnormal fibrillary protein deposition are considered: amyloidosis and fibrillary (immunotactoid) glomerulonephritis. Amyloid is characterised by an antiparallel, beta-pleated configuration which imparts to it a unique apple-green birefringence after Congo red staining. Inspite of its fairly constant physical properties, the chemical composition of amyloid fibrils is amazingly diverse, encomposing AA protein, light chain fragments, transthyretin, procalcitonin, islet amyloid polypeptide, atrial natriuretic peptides, beta-amyloid protein, beta-2-microglobulin, cystatin C, gelsolin, apolipoprotein A1, lyzozyme and their mutant variants. Amyloid P component and heparan sulphate proteoglycan are ubiquitous non-fibrillary amyloid components which have significant roles in the amyloidogenetic process, as do also precursor fibril proteins. Different amyloid fibril proteins relate to different amyloidosis syndromes and different histological patterns, and provide the basis for new diagnostic approaches to this disorder. Glomerular deposits in fibrillary glomerulonephritis (FGN), although often mistaken for amyloid, differ from it in its negative Congophilia, wider fibril width and highly organised, microtubular-tactoidal appearance ultrastructurally. FGN is essentially a primary glomerulopathy resulting in progressive renal failure. Despite certain differences, intriguing similarities between both entities of fibrillary deposition pose a challenge to researchers as to the mechanisms of abnormal protein crystallization and fibril formation in tissues.
  4. Looi LM
    Malays J Pathol, 1994 Jun;16(1):11-3.
    PMID: 16329569
    Congo red screening of routine biopsies at the University Hospital Kuala Lumpur revealed the following categories of amyloidosis: systemic AL (5.9%); systemic AA (3.2%); isolated atrial (14%); primary localized cutaneous (7.5%); other primary localized deposits (3.2%); localized intratumour (58%); and dystrophic (8.6%). Unlike in the West, AA amyloidosis in this population was usually secondary to leprosy or tuberculosis. Liver involvement in AL amyloidosis was shown to exhibit a sinusoidal pattern and differed from the vascular pattern of AA amyloidosis. Within the category of AA amyloidosis, there were two patterns of renal involvement--glomerular and vascular, with the glomerular pattern carrying a more ominous clinical picture. Notable among the localized amyloidoses were isolated atrial amyloidosis complicating chronic rheumatic heart disease, intratumour amyloidosis within nasopharyngeal carcinomas and dystrophic amyloidosis which occurred in fibrotic tissues.
  5. Looi LM
    Malays J Pathol, 1994 Jun;16(1):19-21.
    PMID: 16329571
    An analysis of 1000 consecutive, adequate renal biopsies from patients of the University Hospital Kuala Lumpur between 1982 and 1991 revealed: minimal change nephritis (20.7%), focal glomerulosclerosis (2.9%), proliferative glomerulonephritides (16.0%), membranous glomerulonephritis (5.5%), IgA nephropathy (18.5%), lupus nephritis (24.9%), end stage nephropathy (3.1%) and others (8.4%). Compared with the previous decade, IgA nephropathy has emerged as a common entity. Lupus nephritis forms the largest diagnostic entity and is probably related to the selected referral of SLE patients to this hospital.
  6. Looi LM
    Hum. Pathol., 1993 Jun;24(6):602-7.
    PMID: 8505038
    Congo red screening of 211 consecutive cardiac biopsy specimens obtained during cardiac surgery from 167 patients revealed 26 (16%) instances of isolated atrial amyloidosis (IAA). The ages of IAA-positive patients ranged from 25 to 52 years (mean age, 39 years). Twenty-three (88%) IAA-positive biopsy specimens were from patients with chronic rheumatic heart disease (CRHD) while three (12%) were from patients with an atrial septal defect (ASD). The prevalence of IAA in the CRHD patients was 23%, appreciably higher than that in the ASD patients (15%) and in other patients with atrial biopsies. The prevalence of IAA in both CRHD and ASD patients was significantly higher (P < .001) than in controls. Controls consisted of 247 healthy adults who were autopsied after traumatic deaths, with an age range of 18 to 89 years (mean age, 38 years). Only seven (3%) control subjects were IAA positive; all were over 40 years of age. Isolated atrial amyloidosis deposits were permanganate resistant and immunohistochemically positive for human amyloid P (AP) protein and negative for human amyloid-associated (AA) protein and immunoglobulin light chains. They were observed as fine congophilic and birefringent deposits in intramyocardial vessel walls, along the myocardial sarcolemma, and in the subendocardium. There was associated myocyte hypertrophy but no atrophy. Electron microscopy demonstrated typical nonbranching amyloid fibrils. It is postulated that stretching of the atria in chronic heart disease results in a raised prevalence of IAA. Recent reports that IAA contains atrial natriuretic peptide, a polypeptide hormone product of atrial myocytes, supports this view.
  7. Looi LM
    Australas. J. Dermatol., 1991;32(1):39-44.
    PMID: 1930004
    A review of consecutive biopsies from 85 Malaysian patients with primary localised cutaneous amyloidosis (PLCA) revealed 63 with papular amyloidosis (PA) and 22 with macular amyloidosis (MA). PLCA appeared to affect the Chinese more frequently than the other major ethnic groups but MA was more common than expected among the Indians. Of patients with PA, one had systemic lupus erythematosus, one scleroderma and in another, connective tissue disease was suspected. MA was not found to be associated with any other disease. Histologically, PA differed from MA by the larger size of amyloid deposits in the papillary dermis. There was no difference in their tinctorial and immunohistochemical characteristics. Deposits were permanganate-resistant and negative for AA protein, immunoglobulin light chains and keratin. A few cases exhibited positively for cytokeratin. Strong immunoreactivity for AP protein was observed. PA and MA appear chemically similar and are likely to be of epidermal origin.
  8. Looi LM
    Histopathology, 1991 Aug;19(2):169-72.
    PMID: 1757071
    Seventeen consecutive patients with dystrophic amyloidosis are reported here (eight Chinese, three Indian, three Iban, two Malay and one Caucasian). Ten were females and seven males, with ages ranging from 12 to 80 years (mean of 48 years). Five instances of dystrophic amyloidosis occurred in areas of tissue damage in the cardiovascular system, including fibrotic cardiac valves and an atheromatous plaque. Three occurred in osteoarthritic joint tissue. Of note were three occurrences in endometriotic cyst walls, four in the fibrotic walls of epidermal cysts, one in a hernial sac and one at the edge of a skin ulcer. All deposits were congophilic and exhibited green-birefringence and permanganate-resistance. Immunohistochemistry did not reveal reactivity for AA protein or immunoglobulin lambda or kappa light-chains. AP protein was detected in 35% of cases. Our results show that, besides the usual sites of osteoarthritic joints and damaged heart valves, dystrophic amyloidosis can complicate other areas of chronic tissue damage and fibrosis such as walls of cysts and ulcers. While the pathogenesis and biochemical nature remain unresolved, immunohistochemistry indicates that neither AA nor AL proteins are present in the deposits, and suggests that a different amyloid protein is involved.
  9. Looi LM
    Histopathology, 1991 Feb;18(2):133-41.
    PMID: 1901294
    Congo red screening of 27,052 routine biopsy specimens from 22,827 patients over a 5 1/2-year period in the Department of Pathology, University of Malaya detected 186 cases of amyloidosis. The categories of amyloidosis encountered and their prevalences in relation to each other were: systemic AL (5.9%); systemic AA (3.2%); isolated atrial (14%); primary localized cutaneous (7.5%); other primary localized deposits (3.2%); localized intratumour (58%); and dystrophic (8.6%). A third of patients with systemic AL amyloidosis had coexistent immunocyte abnormality. The commonest underlying pathology for systemic AA amyloidosis was leprosy. Notable among the types of localized amyloidosis revealed by this study were isolated atrial amyloidosis, which appeared to complicate chronic rheumatic heart disease, and intratumour amyloidosis complicating nasopharyngeal carcinoma. Other tumours in which amyloid deposits were observed included basal cell carcinoma, islet cell tumour and medullary carcinoma of the thyroid. Dystrophic amyloidosis was observed in fibrotic tissues, such as damaged cardiac valves and osteoarthritic joints. Heredofamilial amyloidosis, senile systemic amyloidosis and degenerative cerebral amyloidosis were notably absent from this study.
  10. Looi LM
    Ann. Acad. Med. Singap., 1986 Jan;15(1):52-6.
    PMID: 3010797
    Congo red screening of tumour material examined at the Department of Pathology, University of Malaya revealed intratumour deposits of amyloid in 12% of nasopharyngeal carcinomas, 66% of basal cell carcinomas, 100% of medullary carcinomas of the thyroid, 56% of islet cell tumours of the pancreas, 1 out of 16 carcinoids and 1 out of 100 thyroid adenomas. All the deposits were permanganate resistant and did not contain AA protein, indicating that what was encountered was not secondary amyloid. The deposits showed variable staining for immunoglobulin light chains and amyloid P component with a standard peroxidase antiperoxidase method. The possibility that intratumour amyloid has a neoplastic origin is discussed.
  11. Looi LM
    Histopathology, 1989 Feb;14(2):111-20.
    PMID: 2707747
    The histological location of amyloid within various organs in 25 cases of systemic AA amyloidosis was studied with a view to determine whether different morphological patterns exist in this category of amyloidosis. Although morphological variations due to progressive severity of disease were observed, there were appreciable variations in the patterns of amyloid deposition in the kidney and spleen that could not be simply explained on those grounds. Eleven (61%) of 18 kidneys examined showed severe glomerular involvement with mild degrees of vascular deposition while the remaining seven showed predominantly vascular involvement. The glomerular pattern appeared to be more ominous, being significantly associated with severe proteinuria or chronic renal failure. In nine (69%) of 13 spleens examined, amyloid was confined to the walls of small and medium-sized arteries while in the remaining four, vascular involvement was less severe and amyloid was deposited mainly along the reticulin of the white pulp. Possible explanations for these different patterns included resorption and redistribution of amyloid within the body during the course of the disease, and variation in tissue deposition as a manifestation of polymorphism of amyloid proteins. The latter appeared more feasible in view of the recent demonstration of SAA polymorphism and AA heterogeneity in man.
  12. Looi LM
    Cancer, 1983 Nov 15;52(10):1833-6.
    PMID: 6627203
    Congo-red screening demonstrated intratumor deposits of amyloid in 35 of 53 unselected cases of basal cell carcinoma. Male subjects had a higher amyloid positivity rate than female subjects. The amyloid deposits were permanganate-resistant and located in the stroma between clumps of tumor cells, as well as abutting the advancing front of the neoplasm. Solar elastosis was often observed in the overlying and adjacent subepidermis. The relationship between amyloid positivity and the different histological subtypes of basal cell carcinoma, tumor ulceration, and density of the lymphoplasmacytic stromal infiltrate were also studied. The possibility that amyloid originates from the tumor cells and is a result of tumor apoptosis (degeneration) is discussed.
  13. Looi LM
    Histopathology, 1981 Nov;5(6):615-22.
    PMID: 7319480
    Nineteen out of 121 consecutive cardiac biopsies from 107 patients were found to contain amyloid deposits on routine Congo red screening. Seventeen were left atrial appendages removed during mitral valvotomy for chronic rheumatic mitral valve disease while the remaining two were right atrial appendages excised during surgical repair of atrial septal defects. The distribution of amyloid deposits within the atria and their tinctorial characteristics are described. The high prevalence of atrial amyloidosis observed could not be attributed to generalized or senile amyloidosis. The possibility that this is a distinctive localized form of amyloidosis secondary to chronic heart disease is discussed.
  14. Looi LM
    Malays J Pathol, 2008 Jun;30(1):1-10.
    PMID: 19108405 MyJurnal
    The past century has seen tremendous changes in the scope and practice of pathology laboratories in tandem with the development of the medical services in Malaysia. Major progress was made in the areas of training and specialization of pathologists and laboratory technical staff. Today the pathology laboratory services have entered the International arena, and are propelled along the wave of globalization. Many new challenges have emerged as have new players in the field. Landmark developments over the past decade include the establishment of national quality assurance programmes, the mushrooming of private pathology laboratories, the establishment of a National Accreditation Standard for medical testing laboratories based on ISO 15189, and the passing of the Pathology Laboratory Act in Parliament in mid-2007. The Pathology Laboratory Act 2007 seeks to ensure that the pathology laboratory is accountable to the public, meets required standards of practice, participates in Quality Assurance programmes, is run by qualified staff, complies with safety requirements and is subject to continuous audit. The Act is applicable to all private laboratories (stand alone or hospital) and laboratories in statutory bodies (Universities, foundations). It is not applicable to public laboratories (established and operated by the government) and side-room laboratories established in clinics of registered medical or dental practitioners for their own patients (tests as in the First and Second Schedules respectively). Tests of the Third Schedule (home test blood glucose, urine glucose, urine pregnancy test) are also exempted. The Act has 13 Parts and provides for control of the pathology laboratory through approval (to establish and maintain) and licensing (to operate or provide). The approval or license may only be issued to a sole proprietor, partnership or body corporate, and then only if the entity includes a registered medical practitioner. Details of personnel qualifications and laboratory practices are left to be specified by the Director-General of Health, providing for a formal recognition process and room for revision as pathology practices evolve. Encompassed in the responsibilities of the licensee is the requirement that samples are received and results issued through, and management vested in, a registered medical or dental practitioner. This effectively prohibits "walk-ins" to the laboratory and indiscriminate public screening. The requirement for a person-in-charge in accordance with class and speciality of laboratory ensures that the laboratory is under the charge of the pathology profession. Examined carefully, the requirements of the Act are similar to laboratory accreditation, but are backed by legislation. Many of these details will be spelt out in the Regulations, and these in turn are likely to fall back on National professional guidelines, as accreditation does. Although not at first obvious, enforcement of the Act is based on self-regulation by pathology laboratory professionals. Sincere professional input is thus required to embrace its philosophy, ensure rational and transparent enforcement of legislation, and develop National guidelines for good pathology practices upon which enforcement may be based.
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