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Biomedical subjects

W K Ng

Publications and source records attributed to W K Ng.

At least 19 recordsLinked to original sources
PubMed2006

Numerical modelling of biopotential field for detection of breast tumour.

Breast cancer is a disease characterised by the uncontrolled growth of abnormal cells. These cancer cells can travel through the body by way of blood or lymph nodes. Previous studies have indicated that, changes in the electrical properties of abnormal breast are more significant compared to the breast normal tissues. In the present study, a simple 2D models of breast (close to realistic), with and without artificially inserted malignant cancer were simulated, based upon electrical activity within the breast. We developed an inhomogeneous female breast model, closer to the actual, by considering a breast as a hemisphere with various layers of unequal thickness in supine condition. In order to determine the potential distribution developed due to a dipole source, isotropic homogeneous conductivity was assigned to each of these compartments and the volume conductor problem was solved using finite element method. Significant changes in the potential distribution were recoded in the malignant and normal breast regions. The surface potential decreases about 0.5%, for the small malignant region of surface area 13 mm(2) (spherical diameter=2mm). And it (surface potential) decreases about 16.4% for large malignant surface area of 615 mm(2) (spherical diameter=14 mm). Hence, the results show that, the sizes of tumours result in the reduction of surface potential and follows a fourth order polynomial equation. Thus, biofield analysis yields promising results in the detection of the breast cancer of various sizes.

Adult↗
PubMed2002

Thyroid transcription factor-1 is highly sensitive and specific in differentiating metastatic pulmonary from extrapulmonary adenocarcinoma in effusion fluid cytology specimens.

BACKGROUND: Thyroid transcription factor-1 (TTF-1) is a homeodomain-containing transcription factor selectively expressed in thyroid, lung and diencephalon. It has been shown to label pulmonary adenocarcinoma, thyroid tumors, and small cell carcinoma (pulmonary and extrapulmonary) with relatively high sensitivity and specificity. The usefulness of this immunostain in cytology specimens has not been thoroughly discussed in the literature. METHODS: The authors evaluated 36 effusion cytology cases (17 pleural effusion, 18 ascitic fluid, and 1 pericardial effusion) diagnosed as metastatic adenocarcinoma and with cell blocks prepared from the file of Pamela Youde Nethersole Eastern Hospital, Hong Kong, during a three-year period from 1998 to early 2001. The clinical, radiologic, cytologic, and histologic (if any) findings were reviewed. A provisional diagnosis of the primary site was deduced for each of the 36 cases by clinical, radiologic, and/or histologic correlation. Immunohistochemical study was performed on the cell block sections of the effusion cytology specimens using mouse monoclonal antibody against TTF-1, after microwave heat-antigen retrieval. The results were correlated with the primary origin of the metastatic adenocarcinoma. RESULTS: Among the 17 cases of metastatic pulmonary adenocarcinoma, 15 cases showed nuclear staining for TTF-1 in most of the tumor cells (sensitivity, 88.2%). None of the 19 cases of metastatic extrapulmonary adenocarcinoma expressed TTF-1 (specificity, 100%). CONCLUSIONS: The current study validates TTF-1 as a highly sensitive and specific immunomarker for distinguishing between metastatic pulmonary and extrapulmonary adenocarcinoma in effusion cytology specimens, which are known to be associated with intrinsic artifact due to less than ideal cellular preservation.

Adenocarcinoma↗
PubMed2002

Dirofilariasis of breast: report of two cases diagnosed by fine-needle aspiration biopsy.

We report on 2 cases of dirofilariasis of the breast occurring in adult Chinese females residing in Hong Kong. The diagnosis was made by fine-needle aspiration biopsies. The direct smears contained numerous acute inflammatory cells, including eosinophils. A partially necrotic adult nematode of about 400-450 microm in diameter was identified in the cell-block sections of each case. The worm was characterized by a thick cuticle with longitudinal cuticular ridges and fine transverse surface striations, abundant somatic muscle, an intestine, and a reproductive tube or uterus. The morphologic features of this round worm were most compatible with those of Dirofilaria repens. While the clinical and radiologic findings of dirofilariasis of the breast are nonspecific and mimic those of breast neoplasms or inflammatory conditions, a definitive diagnosis is possible with fine-needle aspiration biopsy. A correct diagnosis of dirofilariasis may help to spare patients from unnecessary medical and surgical interventions.

Adult↗
PubMed2002

Peritoneal washing cytology findings of disseminated myxoid leiomyosarcoma of uterus: report of a case with emphasis on possible differential diagnosis.

We report the cytology findings of a rare case of myxoid leiomyosarcoma of the uterus with intraabdominal dissemination. The cytology showed uniformly dispersed spindly to polygonal "epithelioid" tumor cells focally linked by background matrix. Spindly tumor cells attaching to and radiating from branching capillary structures were also present. Occasionally, scattered "signet-ring" cells were found, mimicking metastatic poorly differentiated adenocarcinoma. The background mucoid substance was more conspicuous in the cell block sections. Gross and histologic examination of the surgical specimen revealed a large uterine leiomyosarcoma with prominent myxoid change. Ultrastructural study showed that the "signet-ring" appearance was mainly due to degenerative cytoplasmic change with ballooning of mitochondria, dilatation of endoplasmic reticulum, and elevation of outer nuclear membrane. In contrast to other spindle cell malignancies such as sarcomatoid mesothelioma, sarcomatoid carcinoma, or malignant melanoma, true sarcoma cells in general carry a distinctive cytologic appearance in washing/effusion fluid. In a correct clinical setting, the peculiar association with mucoid matrix and absence of classic lipoblasts should also raise the suspicion of metastatic myxoid leiomyosarcoma.

Aged↗
PubMed2002

Pyothorax-associated large B-cell lymphoma: case report with emphasis on the potential diagnostic challenge.

A rare case of pyothorax-associated large B-cell lymphoma occurring in Hong Kong is reported. The patient was a 64-year-old Chinese male who presented with shortness of breath and pleuritic pain. Radiological examination revealed left pleural thickening associated with bilateral pleural effusion. Open biopsy of the thickened parietal pleura revealed occasional large malignant lymphoid cells of B lineage admixed with fibrin and hyalinised fibrous tissue. These lymphoma cells were shown to harbour both Epstein-Barr virus and human herpesvirus type 8 by in situ hybridisation and immunohistochemical study, respectively. There was no associated lymphadenopathy and hepatosplenomegaly. The clinicoradiological presentation and pathological findings thus fulfilled the criteria of the so-called pyothorax-associated large B-cell lymphoma. Awareness of this rare entity, together with diligent histological examination and proper application of ancillary investigative techniques, are essential for making a correct diagnosis. The co-infection with Epstein-Barr virus and human herpesvirus type 8 in this case also suggests a possible pathogenetic relationship between pyothorax-associated large B-cell lymphoma and primary effusion lymphoma.

Diagnosis, Differential↗
PubMed2001

Crush preparation findings of "sarcomatoid" chordoma of the sacrum: report of a case with histologic, immunohistochemical, and ultrastructural correlation.

We report on the crush preparation findings of a case of "sarcomatoid" chordoma occurring in the sacral region of a 78-yr-old Chinese male. The smears showed clumps and small cords of polygonal tumor cells containing bubbly cytoplasm and round to oval nuclei. Focally, there were also aggregates of long filamentous spindle cells and stellate bizarre cells with marked nuclear pleomorphism. Occasional tumor cells were seen in association with dense amorphous material. Histologic examination of the excised specimen showed features of the so-called "sarcomatoid" chordoma which consisted of prominent foci of mitotically inactive spindle and pleomorphic cells, in addition to the conventional chordoma areas. An osteosarcoma-like pattern of probably metaplastic nature was also seen within the tumor. Immunohistochemical study showed that most tumor cells expressed cytokeratins. Ultrastructural examination revealed the characteristic rough endoplasmic reticulum-mitochondria complexes. While there are many spindle and pleomorphic cells seen in crush preparations, the distinction from other true high-grade malignancies is important. Recognition of these "pseudoanaplastic" cytologic features also helps to expand the morphologic spectrum of chordoma.

Aged↗
PubMed2001

Sclerosing hemangioma of lung: A close cytologic mimicker of pulmonary adenocarcinoma.

We report the fine-needle aspiration biopsy findings of sclerosing hemangioma of lung occurring in a 40-yr-old Chinese woman. Cytologically, there were hyalinized stromal tissue fragments admixed with clusters of nondescript mononuclear tumor cells. Scattered foamy macrophages and red blood cells were also noted in the background. Focal papillary and acinar configurations were seen. However, some of the epithelial cells show nuclear pleomorphism with nuclear hyperchromasia, prominent nucleoli, and occasional intranuclear inclusions. Mitotic activity was virtually absent. The cytologic atypia present may result in misdiagnosis of well-differentiated pulmonary adenocarcinoma, especially bronchioloalveolar carcinoma. Recognition of the subtle cytologic differences, together with cell block examination, immunocytochemistry, and proper clinicoradiologic correlation, is crucial for an accurate preoperative diagnosis.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed2001

Conceptual dilemmas in evaluating individuals with severely impaired consciousness.

States of severely impaired consciousness (SIC) are characterized by cognitive and motor limitations. This case report describes a 45-year-old female with impaired consciousness who began to 'walk'. She initially presented to the hospital unresponsive and was subsequently diagnosed with metabolic encephalopathy due to severe hypoglycaemia. Traditional indices of consciousness indicated a low level of responsiveness; however, during physical therapy, she displayed reciprocal walking movements when lifted to a standing position by two therapists. Despite her ability to walk increased distances during and after neurorehabilitation, she was unable to consistently demonstrate responses indicative of higher levels of consciousness. This case illustrates the challenge of rating patients with limited behavioural repertoire using established measures of impaired consciousness.

Brain Diseases, Metabolic↗
PubMed2000

Sudden death from massive pulmonary tumor embolism due to hepatocellular carcinoma.

Massive pulmonary embolism in cancer patients can be due to detached thrombi or tumor. Pulmonary tumor embolism is often undiagnosed antemortem. We report a 52-year-old Chinese man admitted for management of hepatocellular carcinoma (HCC). Computerized tomography showed tumor involvement of hepatic vein and inferior vena cava. He died suddenly on the day of admission. At autopsy the main pulmonary arteries of both lungs were blocked by large tumor emboli, the immediate cause of death. Although rapid death in patients with HCC is usually caused by intraperitoneal hemorrhage from spontaneous rupture of tumor, massive pulmonary tumor embolism should also be considered in these patients, especially when antemortem evidence of hepatic vein and/or inferior vena cava invasion is present.

Carcinoma, Hepatocellular↗
PubMed1999

Ego-syntonic alien hand syndrome after right posterior cerebral artery stroke.

The alien hand syndrome classically consists of involuntary movements accompanied by a feeling of foreignness and personification of the affected limb. Autocriticism, in which patients criticize and express astonished frustration with the behavior of the autonomous limb, is a commonly noted feature. Most cases of alien hand are associated with lesions of the supplementary motor areas of the frontal lobes, the corpus callosum, or both. The authors report on a 79-year-old man who sustained a right posterior cerebral artery distribution infarction and developed alien hand syndrome in the absence of callosal involvement. Also unique is that the patient perceived the alien hand as acceptable and positive, not hostile and repugnant. This case suggests not only that the neuroanatomic regions responsible for alien hand syndrome may require re-examination, but also that its definition may need expansion.

Aged↗
PubMed1999

Desmoplastic malignant melanoma on the buttock of an 18-year-old girl: differentiation from desmoplastic nevus.

Melanocytic proliferation in young people may sometimes pose a diagnostic dilemma. This is particularly so when a desmoplastic component is present. Because the two main differential diagnoses, desmoplastic malignant melanoma and desmoplastic Spitz nevus, share some morphologic features, the diagnosis of desmoplastic malignant melanoma may be overlooked. Distinction between the two is important because they show completely different biological behavior. The age of patient, site of lesion, histologic findings of melanocytic atypia, neurotropism, mitosis, and maturation help to distinguish the two entities. We report a case of desmoplastic malignant melanoma occurring in the buttock of an 18-year-old Chinese girl. Histologically, it had typical features of desmoplastic malignant melanoma with junctional melanocytic atypia and prominent neurotropism. Clinical and histologic differences between desmoplastic malignant melanoma and desmoplastic Spitz nevus are reviewed. We conclude that although desmoplastic Spitz nevus occurs much more commonly in adolescents, desmoplastic malignant melanoma can occur in this age group and even in non-sunexposed skin. Microscopic findings remain the mainstay that guides the final diagnosis.

Adult↗
PubMed1999

Creating a model for fabricating a partial hand glove prosthesis using the realigned casts of the contralateral digits.

A method for creating a model for fabricating a partial hand glove prosthesis is described. The realigned casts of the corresponding digits of the contralateral uninjured hand were used to substitute for the lost digits on a cast of the stump. The technique allows an exact reproduction of the anatomical and fine surface details of the digits. It has the advantage of customisation, allowing a close match in the size, shape and surface characteristics of the prosthesis to that of the remaining digits of the hand.

Adult↗
PubMed1999

Metamerism in aesthetic prostheses under three standard illuminants--TL84, D65 and F.

This study looks at the effect of metamerism in colour-matching and the assessment of multi-layered silicone rubber finger prostheses. The aim was to identify the choice of illuminants for colour matching the prostheses that would give rise to the least metameric effect between the prostheses and the human skin or the best colour match. The prostheses were prepared and colour matched to a fair-skinned subject under 3 reference illuminants--TL84, D65, F and a combination of illuminants--TL84, D65 and F. The prostheses were then measured for colour using a spectrophotometer based on the CIE indices L*, a*, b* with each prosthesis assessed separately against the subject's index finger under the reference illuminants--TL84, D65 and F. The prostheses were also assessed by a panel of 50 observers and scored according to colour-match. Colour differences between the skin and prosthesis were measured in the illuminant under which the prostheses were prepared and then under the other reference illuminants. A relationship was obtained between the measured mean colour difference, deltaE*, and the mean visual assessment score for each prosthesis. This paper points out the concerns related to the optical phenomenon of metamerism with the colour pigments used. This can affect the colour match of the prosthesis as perceived by the patient. The findings seem to suggest that this metameric colour difference can be minimised if the prosthesis is matched under a combination of lights, which were found to give the best-perceived match.

Fingers↗