Since this text is visible on the main page, first some thoughts on assimilation tubules: Their purpose is to inject nanoprobes in the bloodstream of a victim. As far as I know, they are "one-way": The tubules don't take any material from the victim. And it wouldn't be smart if they did: Assume the victim is infected with something, the attacking Borg can't handle. Then the drone might die. Ok, no-one will shed a tear about it, but the whole point of assimilation is to increase in numbers...
So, in VOY Endgame Janeway injects herself a neurolytic pathogen, which
kills the Borg-Queen after she plunges her assimilation tubules into Janeways throat.
How is that possible? The neurolytic pathogen appears to be a (liquid) physical agent. Somehow that agent must
enter the queen's bloodstream. It doesn't help much, that Janeway is assimilated now. Granted: The agent is in a manner of speaking now "part of the collective" somehow, since Janeway is part of the collective.
But that doesn't explain anything. It can't be distributed via the hive mind, which is in essence a subspace radio and can't transmit liquids. So how is that possible?
If it helps: A similar question could probably be raised concerning Icheps special "gift".