Keisuke Nishihara

Tottori University, Tottori, Tottori-ken, Japan

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Publications (9)24.4 Total impact

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    ABSTRACT: It is important to know whether a parotid gland lesion is in the superficial or deep lobe for preoperative planning. We aimed to investigate the ability of 3.0 T magnetic resonance (MR) imaging with surface coils to identify the intraparotid facial nerve and locate parotid gland lesions, in comparison to other indirect landmark methods. We retrospectively evaluated 50 consecutive patients with primary parotid gland lesions. The position of the facial nerve was determined by tracing the nerve in the stylomastoid foramen and then following it on sequential MR sections through the parotid gland. The retromandibular vein and the facial nerve line (FN line) were also identified. For each radiologist and each method, we determined the diagnostic ability for deep lobe lesions and superficial lobe lesions, as well as accuracy. These abilities were compared among the three methods using the Chi-square test with Yates' correction. Mean diagnostic ability for deep lobe lesions, the diagnostic ability for superficial lobe lesions, and accuracy were 92%, 86%, 87%, respectively, for the direct identification method; 67%, 89%, 86%, respectively, for the retromandibular vein method; and 25%, 99%, 90% , respectively, for the FN line method. The direct identification method had significantly higher diagnostic ability for deep lesions than the FN line method (Pā€‰<ā€‰0.01), but significantly lower diagnostic ability for superficial lobe lesions than the FN line method (Pā€‰<ā€‰0.01). Direct identification of the intraparotid facial nerve enables parotid gland lesions to be correctly located, particularly those in the deep lobes.
    Neuroradiology 11/2010; 52(11):1037-45. · 2.70 Impact Factor
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    ABSTRACT: magnetic resonance (MR) imaging of parotid gland tumors has been widely reported, although few reports have evaluated the capsule of parotid gland tumors in detail. to evaluate the diagnostic usefulness of 3.0 T MR imaging with surface coils for detection of the parotid gland tumor capsule, and to clarify the characteristics of the capsules. seventy-eight patients with parotid gland tumors (63 benign and 15 malignant) were evaluated. Axial and coronal T2-weighted and contrast-enhanced T1-weighted images were obtained using a 3.0 T MR scanner with 70 mm surface coils. It was retrospectively assessed whether each parotid gland tumor was completely surrounded by a capsule. The capsule was classified as regular or irregular in terms of capsular thickness, and as none, mildly, or strongly enhancing in terms of contrast enhancement. Visual interpretations were compared with histopathological findings to evaluate the diagnostic ability of MR imaging to detect parotid gland tumor capsules. Statistical evaluation was conducted concerning the presence of capsules, capsular irregularity, and the difference in contrast enhancement between benign and malignant tumors, and that between pleomorphic adenomas and Warthin's tumors. capsules completely surrounding the tumor on MR imaging yielded a sensitivity of 87.7% (50/57), specificity of 90.5% (19/21), and accuracy of 88.5% (69/78). Benign tumors had a capsule completely surrounding the tumor significantly more often than malignant tumors (P = 0.009). Concerning capsular irregularity, malignant tumors tended to have more irregular capsules than benign tumors, although there were no significant differences. The capsules of malignant tumors enhanced significantly more strongly than those of benign tumors (P = 0.018). 3.0 T MR imaging using surface coils could correctly depict parotid gland tumor capsules in most cases. Most benign and some malignant tumors had capsules completely surrounding the tumors. Malignancy should be considered in tumors with irregular and strongly enhancing capsules.
    Acta Radiologica 10/2010; 51(10):1103-10. · 1.33 Impact Factor
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    ABSTRACT: Geminin negatively regulates Cdt1 and induces the formation of prereplicative complexes by loading mini-chromosome maintenance proteins (Mcm) onto chromatin and limiting DNA replication to once per cell cycle. Recent studies have suggested that geminin expression is a marker of the S/G2/M phase of the cell cycle and is associated with a poor prognosis in various human malignancies. This study aimed to clarify the pathobiological role of geminin in intestinal-type gastric carcinoma, and its relationships with minichromosome maintenance 2 (Mcm2) and Ki67 expression. We performed western blot analysis of seven human gastric cancer cell lines, and immunohistochemical analysis of 72 gastric mucosal lesions and 128 surgically removed advanced intestinal-type gastric carcinomas. Double-labeling immuno-fluorescence was performed to identify the coexpression of geminin and Ki67. Geminin was detected in all cell lines. Geminin labeling indices (LIs) in hyperplastic polyps, low-grade adenomas, high-grade adenomas, and intestinal-type adenocarcinomas were 3.9%, 10.5%, 18.6%, and 27.2%, respectively. The equivalent LIs for Ki67 and Mcm2 were 17.7%, 42.2%, 52.6%, and 59.7%; and 26.7%, 70.0%, 67.8%, and 77.8%, respectively. Double-labeling immunofluorescence revealed coexpression of geminin and Ki67 in both normal and tumor cells. The LI for geminin was significantly correlated with N stage, International Union Against Cancer (UICC) stage, Mcm2 LI, and Ki67 LI. Patients in stages I-IV and stage III with higher LIs for geminin (>25%) had significantly worse prognoses (P < 0.05 and P < 0.04, respectively). Univariate Cox regression analysis indicated that the overall survival of stage I-IV tumors was significantly correlated with high geminin LIs (relative risk [RR] = 1.94; P = 0.04). Geminin expression might reflect the biological nature of gastric intramucosal neoplasms and could be a possible prognostic marker in advanced intestinal-type gastric carcinomas.
    Gastric Cancer 08/2010; 13(3):177-85. · 3.99 Impact Factor
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    ABSTRACT: DNA should be duplicated precisely once per cell cycle to maintain genome integrity. After DNA replication, geminin binding to Cdt1 inhibits uploading of the minichromosome maintenance (MCM) complex as DNA helicase onto chromatin and prevents DNA re-replication in the same cell cycle. Expression of geminin indicates poor prognosis in some malignancies, such as breast and renal cell carcinoma. We evaluated the expression of geminin to clarify its pathobiological and prognostic significance in colorectal cancer, compared with expression of MCM7 and Ki-67. We performed Western blot analyses of 5 human colorectal cancer cell lines and immunohistochemistry on 191 surgically removed specimens of Dukes' B and C stage colorectal cancer. Double-labeling immunofluorescence was also carried out to identify co-expression of geminin, MCM7 and Ki-67. Geminin proteins were detected in all the 5 cell lines examined. Geminin, MCM7 and Ki-67 were co-expressed and cells that stained only for geminin were not detected. Mean labeling indices (LIs) for geminin, MCM7 and Ki-67 were 26.3, 58.2 and 40.8%, respectively. Patients with high geminin LIs had significantly unfavorable prognosis in stage II and III colorectal cancer (P=0.04). Patients with a tumor with a higher proliferating nature (i.e. high LIs for three markers) showed significantly unfavorable prognosis in multivariate Cox analysis. Our results indicate that assessment of geminin, MCM7 and Ki-67 may be useful for predicting prognosis in patients with colorectal cancer.
    Oncology Reports 06/2009; 21(5):1189-95. · 2.30 Impact Factor
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    ABSTRACT: Minichromosome maintenance (MCM) proteins, essential molecules in the initiation and elongation of DNA replication, have been considered to be good indicators of cell proliferation. We examined the expressions of MCM7 and Ki-67 in lung adenocarcinomas (ACs) with a diameter less than 3cm (pT1), to clarify their pathobiological significance. Immunohistochemistry was conducted to obtain labeling indices (LIs%) for MCM7, MCM2 and Ki-67 in 100 surgically removed pT1 ACs. The LIs were compared with clinicopathological profiles and overall survival rates. The mean LIs of MCM7 and Ki-67 were 20.2+/-15.2% and 13.7+/-11.2%, the value being higher in the former than in the latter (P<0.01). MCM7 LIs were significantly correlated with sex, histological grade, histological subtype, tumor size, LIs of Ki-67, MCM2 and P53 (P<0.05). LIs of MCM7 and Ki-67 were significantly higher in the 84 non-bronchioloalveolar carcinomas than in the 16 bronchioloalveolar carcinomas (P<0.01). Kaplan-Meier survival curves showed that patients with higher MCM7 LIs had poorer prognosis in the 100 pT1 ACs as well as in the 73 stage I ACs. Multivariate Cox regression analysis confirmed that the LIs of MCM7, but not the LIs of MCM2 and Ki-67, was an independent prognostic marker in the 73 stage I ACs. These results suggest that MCM7 is an independent prognostic marker, being more reliable than MCM2 or Ki-67 in human pT1 ACs as well as in human stage I ACs.
    Lung cancer (Amsterdam, Netherlands) 01/2009; 65(2):223-9. · 3.14 Impact Factor
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    ABSTRACT: To clarify the diagnostic accuracy of diffusion-weighted imaging (DWI) in differentiating benign from malignant ovarian lesions. We retrospectively analyzed magnetic resonance images of 123 ovarian lesions in 119 patients. We defined lesions with abnormal signal intensity as malignancy and assessed the location of abnormal intensity within the lesions on DWI. We also assessed the mean and lowest apparent diffusion coefficient (ADC) values of the solid portion for each ovarian lesion. The majority of malignant ovarian tumors and mature cystic teratomas, and almost half of the endometriomas, showed abnormal signal intensity on DWI, whereas most fibromas and other benign lesions did not. The main locations of abnormal signal intensity were solid portions in malignant ovarian tumors, cystic components suggestive of keratinoid substances and Rokitansky protuberance in mature cystic teratomas, and intracystic clots in endometriomas. On DW imaging, receiver-operating characteristic analysis yielded mean Az values of 0.703. There was no significant difference in mean and lowest ADC values between malignant and benign lesions. DWI of ovarian lesions and ADC values of the solid component are not useful for differentiating benign from malignant ovarian lesions. This knowledge is essential in avoiding misinterpretation in the diagnosis of ovarian lesions.
    Journal of Magnetic Resonance Imaging 12/2008; 28(5):1149-56. · 2.57 Impact Factor
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    ABSTRACT: Minichromosome maintenance (MCM) proteins are essential components for DNA replication, and also prognostic markers for various human tumors. MCM-positive but Ki67-negative cells (e.g. primary oocytes) are thought to be licensed non-proliferating populations, and are significantly correlated with the clinicopathological profiles of some human tumors. In the present study, we evaluated the expression levels of MCM7, MCM2 and Ki67 in colorectal cancer to clarify their pathobiological significance. We carried out Western blot analyses of 5 human colorectal cancer cell lines and performed immunohistochemistry on 202 surgically removed colorectal cancers of Dukes' B and C stages. Double-labeling immunofluorescence was also carried out on the cancer specimens to identify MCM-positive but Ki67-negative tumor cells. MCM proteins were detected in all the 5 cell lines examined. MCM7 and MCM2 were coexpressed in almost the same populations of tumor cells, whereas MCM7-negative but Ki67-positive tumor cells were absent in the double-labeled specimens, except for mitotic cells. The mean positive tumor labeling indexes (LIs) for MCM7, MCM2 and Ki67 were 58.1, 57.1 and 40.6%, respectively. The mean LI for MCM7-positive but Ki67-negative tumor cells was 17.6%, and significantly correlated with the N status (P=0.01), distant metastasis (P=0.01) and UICC stage (P=0.02). The high LI of >58.1% for MCM7 were independent prognostic factors in multivariate Cox regression analysis (relative risk = 2.12; P=0.02). Our results indicate that MCM7 expression is an independent prognostic factor for human colorectal cancer, and MCM7-positive but Ki67-negative tumor cells are correlated with tumor metastases.
    International Journal of Oncology 08/2008; 33(2):245-51. · 2.66 Impact Factor
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    ABSTRACT: Patients receiving long-term hemodialysis tend to develop renal cell carcinoma (RCC). Among such cases, chromophobe RCC and so-called 'capsulomas' are rarely reported. Here, we report a case of a Japanese woman in her early 70s, who developed both renal lesions after 17 years of hemodialysis. The patient received radical nephrectomy for enlarging renal mass. Grossly, the resected kidney showed a dominant tumor and small-sized subcapsular nodules. Histologically, two types of neoplasm, chromophobe RCC and 'capsuloma', existed with acquired cystic disease of the kidney. Chromophobe RCC had eosinophilic cytoplasm with perinuclear halos, and some tumor cells showed oncocytic features. Hale's colloidal iron staining showed a weakly positive cytoplasmic reaction. Immunohistochemistry was diffusely positive for cytokeratin 7, but negative for vimentin in the tumor cells. 'Capsulomas' were multiple subcapsular nodules composed almost entirely of smooth muscle-like cells with immunoreactivity for melanosome-associated antigen detected by HMB-45.
    International Journal of Urology 07/2008; 15(6):543-5. · 1.73 Impact Factor
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    ABSTRACT: The origin licensing factor minichromosome maintenance 2 (MCM2) has recently been identified as a critical regulator of proliferation in both normal and neoplastic cells. This study examined whether MCM2 expression was of prognostic relevance in patients with stage III gastric carcinoma and whether the expression of this marker showed any correlation with clinicopathological characteristics. In addition, we evaluated whether the expression of this proliferation marker was correlated with that of another marker, Ki-67, in gastric carcinoma. We examined the immunohistochemical expression of MCM2, Ki-67, and p53 in 103 surgically removed stage III gastric carcinomas, which consisted of 60 intestinal-type and 43 diffuse-type carcinomas. The labeling indices (LIs) of MCM2 and Ki-67 in cancer cells were compared with clinicopathological characteristics, p53 expression, and overall survival rates. The mean MCM2 and Ki-67 LIs were 69.1 +/- 11.8% and 48.2 +/- 14.5%, respectively, in the intestinal carcinomas, and 43.7 +/- 9.9% and 24.9 +/- 11.0%, respectively, in the diffuse carcinomas. The LIs of these proteins revealed no significant association with clinicopathological characteristics or with p53 expression in the carcinomas. Kaplan-Meier survival curves showed that, in the patients with diffuse carcinoma, those with higher MCM2 LIs had a poorer prognosis (P < 0.05), but the MCM2 LI was not correlated with prognosis for those with intestinal carcinoma (P = 0.25). Ki-67 expression had no significant correlation with prognosis in either intestinal-type or diffuse-type carcinomas. Multivariate Cox regression analysis confirmed that MCM2 was an independent prognostic factor in patients with diffuse carcinoma. Our data suggest that MCM2 is a useful prognostic marker in patients stage III diffuse-type gastric carcinoma.
    Gastric Cancer 01/2008; 11(1):37-46. · 3.99 Impact Factor