...This is the question...
"...What exactly IS a subcortical cyst anyway?"
http://www.ctsplace.com/cts_board/post-4915.html
Cortex of a bone is the thick external layer.
Subcortical is something just under the cortex, in the spongy matrix of the bone.
Cysts may be of different nature (chronic inflammation, etc.)
ikod [;D]