Hello, thanks for the query to H.C.M.
Here I would like to say that forget about cancer as you mentioned in your's query.
Skin folds in our body are most prone to skin infections and that's it is .
Multiple boils commonly known as pyoderma
are most frequent among few persons , however reasons are different.
Poor hygiene is the most common cause as in buttock region there are folds between lower part of buttock and upper part of back of thigh.
Due to poor hygiene there are growth of bacteria hence boils.
Another reason of frequent boils
type 1 or 2
2. Worm infestation
3. Precursor of dermatitis
So please get in blood examination for above mentioned reasons and consult a doctor and have a treatment accordingly.
Good luck. Dr. HET