It could be made an optional `latex` USE flag. If those packages are not installed, cantor displays raw LaTeX in the GUI. There is no error messages or warnings, it just dump raw LaTeX.
Debian equivalent bug report http://forums.debian.net/viewtopic.php?f=6&t=104976
Thanks for your report, fixed in 40dd87b57b14c0f695529c786e59404e648f83a1 (added einfo about LaTeX support)