can you help to me?

[CACTI1]

hello guys, what is this brown section on my plants? and why do they grow?
What I do?

[iann]

Corking.
http://cactiguide.com/cactipests/#corking" onclick="window.open(this.href);return false;

Excessive amounts of corking indicate a problem, often just poor growing conditions but sometimes a pest like mites.

[juliab]

I know how it is to have to watch ever cactus under the microscope sort of a way to describe how I do.....I have this same cactus, also I been told leave it be its drying over and it will be OK well that was a year ago it sort of got a leaning growth to it but hey when I re-pot I am going to try to straighten it up. I dont know if this will help you but as long as its green just set and watch it. I hate to throw away anything that still as life in it.

Good luck let us know how its doing.