Paper for software tool - Medical Domain This is really related to this question (Creating paper on software tool). 

But there was this comment there which asked for more details about the software's domain.

I created (still in beta stage) a software for Brain Tumor, but I would like to publish (if possible) about the software itself and not so much on the validation of it. (This would be eventually a later paper).  

What's is the best approach for publishing about this software "proposal" for usage in medical clinics? 

My concern is that while it's being tested. It wasn't tested enough for a full paper, but I still want to publish it.
If you want to publish software in a quality scientific journal it is usually required that it represents a significant advance over previously published software, which is usually demonstrated by direct comparison with available related software. There will be no way to get around this.

I would also recommend to put the code on github (http://github.com). Github is more and more recognized as THE resource for code hosting. It is a free service for public repositories, and it is widely accepted in the community, e.g. you can register your Github repos with Impactstory (http://impactstory.org).

"Source Code for Biology and Medicine" (http://www.scfbm.org) might be an appropriate journal for you.