[Zope] Content-Type missing for uploads?

[Alex]

How can I get the Content-Type of a file that has been uploaded with a form?

example:

<form method="post" enctype="multipart/form-data">
<input type="file" name="myfile">
<input type="submit">
</form>

when you upload a file with this form, the browser sends the Content-Type of
"myfile" , the question is: How can I get that Content-Type information from
zope?

By the way,  it's not REQUEST.CONTENT_TYPE, as this is set to
multipart/form-data.

any ideas??
Thanks

Alex