Several molecular and histopathological prognostic markers have been proposed for the therapeutic stratification of medulloblastoma patients. Amplification of the c-myc oncogene, elevated levels of c-myc mRNA, or tumor anaplasia have been associated with worse clinical outcomes. In contrast, high TrkC mRNA expression generally presages longer survival. The goal of this study was to evaluate the prognostic value of c-myc, N-myc and TrkC expression in medulloblastomas and compare them to histopathological classification. We used in situ hybridization to measure expression of these molecular markers. c-myc mRNA was detected in 18 of 59 (31%) cases, and was significantly associated with shorter patient survival times on both univariate and multivariate analyses (p = 0.04). The presence of c-myc mRNA was also significantly associated with tumor anaplasia. While survival rates were higher for patients with low N-myc or high TrkC expression, these differences were not statistically significant. The group of patients with either moderate or severely anaplastic tumors showed only a trend towards shorter survival (p = 0.11). However, severe anaplasia alone was significantly prognostic (p = 0.002). Given the prognostic import of c-myc, we investigated 2 potential mechanisms by which its expression might be regulated: Wnt signaling and Mxi-1 mutation. Nuclear translocation of beta-catenin, a marker of Wnt pathway activation, was more common in medulloblastomas with high c-myc than in tumors overall, but the difference was not statistically significant. No Mxi-1 mutations were detected in the 22 cases examined. The association we describe between c-myc expression, tumor anaplasia, and worse clinical outcomes provides further evidence for the importance of this oncogene in medulloblastoma pathobiology.

After 2 decades of observation with close follow-up, the St Jude Medical mechanical valve continues to be a reliable prosthesis.

BACKGROUND Standard mitral valve replacement (MVR) in patients with chronic mitral regurgitation consistently results in a decrease in postoperative left ventricular (LV) ejection performance. This fall in ejection performance has been attributed, at least in part, to unfavorable loading conditions imposed by the elimination of the low-impedance pathway for LV emptying into the left atrium. In contrast to standard MVR in which the chordae tendineae are severed, however, MVR with chordal preservation (MVR-CP) does not usually decrease LV ejection performance despite similar removal of the low-impedance pathway. The purpose of the present study was to define the mechanisms responsible for this discordance in postoperative ejection performance between MVR with and without chordal preservation. METHODS AND RESULTS Echocardiography and sphygmomanometer blood pressures were obtained in 15 patients with pure chronic mitral regurgitation before and 7-10 days after mitral valve surgery. These measurements were used to calculate ventricular volume, wall stress, and ejection fraction. Seven patients underwent MVR with chordal transection (MVR-CT), and eight patients underwent MVR-CP. MVR-CT resulted in no postoperative change in LV end-diastolic volume, a significant increase in LV end-systolic volume, a significant increase in end-systolic stress, from 89 +/- 9 to 111 +/- 12 g/cm2 (p < 0.05), and a significant decrease in ejection fraction, from 0.60 +/- 0.02 to 36 +/- 0.02 (p < 0.05). In contrast, patients who underwent MVR-CP had a significant decrease in LV end-diastolic and end-systolic volumes. End-systolic wall stress actually fell from 95 +/- 6 to 66 +/- 6 g/cm2 (p < 0.05), and ejection fraction was unchanged (0.63 +/- 0.01 before and 0.61 +/- 0.02 after mitral valve surgery) instead of reduced. CONCLUSIONS MVR-CT resulted in a decrease in ejection performance caused in part by an increase in end-systolic stress, which in turn increased end-systolic volume. Conversely, MVR-CP resulted in a smaller LV size, allowing a reduced end-systolic stress and preservation of ejection performance despite closure of the low-impedance left atrial ejection pathway.

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