Arthur W Clark

The University of Calgary, Calgary, Alberta, Canada

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Publications (5)14.59 Total impact

  • Jian-Qiang Lu, Arthur W. Clark
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    ABSTRACT: Tumor-to-tumor metastasis (TTM) is a relatively rare but well-documented phenomenon. When malignant tumor metastasizes to an intracranial tumor, meningiomas are most often the recipient; and breast or lung carcinoma the most common donor (primary tumor). The diagnosis of TTM can be made only by histopathological examination. Awareness of TTM is essential in clinical practice for timely diagnosis and early detection of malignant disease. The pathogenesis of TTM is related to various factors including vascularity and indolent growth of the recipient tumor; and simultaneous occurrence of the particular donor and recipient tumors (most notably breast carcinoma and meningioma). Most essential for understanding pathogenesis, however, are current concepts in the pathogenesis of metastatic cancer, an edifice rising on the concept of “seed and soil” expressed by Paget in 1889. The recently developed metastatic niche model is built on “seed and soil” theory, and describes the evolution of a conducive microenvironment in which disseminated tumor cells engraft and proliferate at the secondary sites. Early interventions that target both the disseminating seed and the metastatic soil may enable improvements in prognosis of malignant tumors. KeywordsMetastasis-TTM-Extracranial-Intracranial-Pathogenesis-Gliomas
    12/2010: pages 35-46;
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    ABSTRACT: To evaluate the effects of allogeneic hematopoietic stem cell transplantation (allo-HSCT) on the brains of persons with and without multiple sclerosis (MS) by means of postmortem histopathological examination. Postmortem histopathology, case studies, and case-control studies. Patients Four patients with MS who died at a median of 4.5 months (range, 3-9 months) after allo-HSCT for a concomitant hematologic malignant neoplasm; 5 patients without MS who died at a median of 10.0 months (1-29 months) after allo-HSCT; and 5 control subjects without MS who did not undergo allo-HSCT. Referral centers. Intervention Allogeneic hematopoietic stem cell transplantation. Morphological features and immunohistochemical features, including the quantitative measures of chronic inflammatory cells. Demyelinating and inflammatory activities of MS persisted after allo-HSCT in all of the patients with MS. Active and chronic active MS lesions exhibited significantly higher numbers of CD3+ T cells and CD8+ cytotoxic T cells and significantly higher scores of CD68+ microglia/macrophages than did chronic inactive lesions or normal-appearing white matter. The normal-appearing brains of allo-HSCT recipients who did not have MS were found to have significantly higher numbers of CD3+ T cells and CD8+ cytotoxic T cells and higher scores of CD68+ microglia/macrophages compared with the controls; however, no demyelination was identified in these non-MS samples. Allo-HSCT fails to halt the demyelination and inflammation of MS.
    Archives of neurology 06/2010; 67(6):716-22. · 7.58 Impact Factor
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    ABSTRACT: The clinicopathological spectra of a dysembryoplastic neuroepithelial tumor (DNT) and a rosette-forming glioneuronal tumor (RGNT) are expanding. We report here the autopsy findings of a case of complex glioneuronal tumor with combined histological features of both a DNT and an RGNT. A 79-year-old man presented with a 1-month history of confusion and gait difficulties. A magnetic resonance imaging scan revealed obstructive hydrocephalus attributed to a mass in the posterior third ventricle. A third ventriculostomy was performed. Postoperatively, the mass remained unchanged in size for more than 14 months. Thirty-eight months after his initial manifestations, he experienced minor head trauma and was then hospitalized. Despite placement of an external ventricular drain and other supportive treatment, he deteriorated and died. A full autopsy was performed, with emphasis on the brain. The mass lesion and a few independent microfoci situated primarily around the third ventricle showed histological features of pilocytic astrocytoma with recurrent hemorrhage. Far more numerous were microfoci with histological features of a DNT, including floating neurons, as well as typical RGNT-associated, synaptophysin-positive rosettes and perivascular pseudorosettes. The advanced age of the patient, the coexisting histological features of the DNT and RGNT, and the distinctive anatomic distribution of the lesions, being centered on the third ventricle, may lend insight into the histogenetic relationship of a DNT, an RGNT, and mixed glioneuronal tumors.
    Neurosurgery 07/2009; 64(6):E1193-5; discussion E1195. · 2.53 Impact Factor
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    ABSTRACT: Tumor-to-tumor metastasis (TTM) is a relatively rare but well-documented phenomenon. The authors report a unique case of esophageal carcinoma metastatic to an intracranial paraganglioma. A sellar and suprasellar tumor was found using MR imaging in an 81-year-old man who presented with a 3-week history of progressive headache and blurred vision. A subtotal excision of the tumor was achieved. Histopathological examination of the tumor disclosed a neoplasm with two distinct components: one showing the classic Zellballen pattern of a paraganglioma, the other exhibiting malignant features leading to the diagnosis of a poorly differentiated carcinoma metastatic to a sellar/suprasellar paraganglioma. The primary esophageal carcinoma was not uncovered until 2 months later, after the patient presented with upper gastrointestinal bleeding. The patient died 4 months after initial presentation. This case expands the spectrum of TTM, and emphasizes the importance of TTM in the practice of pathology.
    Journal of Neurosurgery 01/2009; 110(4):744-8. · 3.15 Impact Factor
  • The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 04/2008; 35(1):111-4. · 1.33 Impact Factor