I've never had a problem with spots/black heads but I had a giant (when I say giant, I mean giant) cyst on my stomach once which I got popped and drained at hospital because otherwise it would have popped by itself and got infected. It was then stuffed and bandaged up, it needed to be stuffed at the hole was so large that it wouldn't have healed normally otherwise.
For about a month afterwards I had to attend a GP every week to get the stuffing removed, have the hole cleaned out and then stuffed again. The first time I had it done I collapsed on my way out of the surgery as it was f***ing horrific.
I thought this was the worst it would get, then a few months later I got another one on the perineum but luckily this burst on its own and didn't get to that extent.
Apparently cysts are caused by poor blood of some sort, possibly diabetes but I checked out OK and haven't had any since.
Edit: I now have two scars on my stomach, one for cyst and one for appendix, and it looks badass (or I like to think so).