An ulcer that may develop in burn tissue is
Marjolins
Rodent
Melanoma
Curlings
Marjolin's ulcer is the name given to a malignancy (usually sq cell ca) which arises in a:

any long-standing wound or
a scar: eg scar of an old burn


It presents the following characteristics
It grows slowly as the scar is relatively avascular
It is painless as scar tissue contains no nerves.