Like most cancers, it is thought to begin in a single cell, with a mutation that is not present at birth but that occurs later for some unknown reason.

我们认为该病与大多数癌症一样，是起源于单个细胞突变，但这种突变并不是先天的，而是发生于后天，但原因不明确。

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Methods The level of expression of CD44 in 41 unknown reason infertility and 35 normal endometrium was measured by immunohistochemical method (S-P technique).

方法：采用免疫组化s - P法检测41例不明原因不孕症及35例正常宫内膜组织中CD 44的表达水平及分布。

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The patient of convulsion with unknown reason, and no fever, should be checked the blood-lead for early diagnosis in order to prevent from leaking diagnosis.

对不明原因的无热惊厥者应注意及时行血铅检查，以便早期诊断，防止漏诊。

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Tobey Maguire, looking ever more costive and uncomfortable, returns as Peter Parker, who finds himself doubly transformed first into the crime-busting arachnid whom we know and revere, second into a black-suited alternative who revels in violence and, for some unknown reason, keeps breaking into dance moves.

NEWYORKER: Spider-Man 3

The reason all money would initially go into money market accounts is a largely unknown peculiarity in the way the feds now keep Social Security records: Employers send in Social Security taxes in lump sums periodically throughout the year.

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