Marjolin's ulcer is:

Marjolin's ulcer is a low grade squamous carcinoma which develops on a chronic benign ulcer or a long standing scar tissue. It is slow growing as scar tissue is relatively avascular and is also painless as there are no nerves in scar tissue. Secondary deposits are not found in the regional lymph nodes as there are no lymphatics in the scar tissue. If the ulcer invade the normal tissue, only the regional nodes can be involved by lymphatic spread. Ref: Applied Basic Science For Basic Surgical Training By Andrew T.Raftery, Page 49 ; Bedside Clinics In surgery By M.L Saha, 2006, Page 312