Nothing in kde-base/thumbnailers-4.10.5 links to lcms.
Thanks, fixed in CVS and git. + 31 Jul 2013; Michael Palimaka <kensington@gentoo.org> + thumbnailers-4.10.4.ebuild, thumbnailers-4.10.5.ebuild: + Remove unused lcms dependency wrt bug #478410. http://git.overlays.gentoo.org/gitweb/?p=proj/kde.git;a=commit;h=9f5478882a150390f717ec47966c23c85f8ef1aa