What is burn scar carcinoma?

I had a third degree burn on my left knee as a child.The Dr told me there is a possibility there is a burn carcinoma now. What is this? I know carcinoma is cancer but I had never heard of this before.

SUMMARY. Marjolin's ulcer is defined as a malignant, ulcerating neoplasm occurring in cicatricial tissue, and is thought to be more aggressive than the other more common varieties of skin cancers. It has been reported in chronic scars of diverse origins. The following report describes two cases of burn scar carcinoma. A review is made of the literature pertaining to the mechanisms, paihological findings, clinical presentation, prognosis, prevention and treatment of this malignant degeneration of burn scars.

Introduction
The association between thermal burn scars and neoplasia was initially recognized by Celsus in AD 100 (Treves and Pack, 1930). Jean Nicolas Marjolin, writing in 1828, is widely credited with the first description of tumour arising in bum scars (Marjolin, 1828). It was De Costa in 1903 who first coined the term "Marjolins's ulcer", applying it to tumours arising in simple leg ulcers. Although Steffen (1984) and Nancarrow (1983) have pointed out that Marjolin probably did not recognize the malignant nature of these ulcers, most other authors have all iden'tified the malignancy found in burn scars such as Marjolin's ulcer. Today the term "Marjolin's ulcer" is used to describe malignant turnours arising in many different types of cutaneous scars and chronic wounds, such as bum scars, chronic venous ulcers, pressure ulcers (decubitus ulcers), osteomyelitis sinuses, urinary fistulas, pilonidal sinuses, gummata, smallpox vaccination scars and radiation scars (Abbas and Beecham, 1988; Barr and Menard, 1983; Berkwits et al., 1986; Fishman and Parker, 1991; Nancarrow, 1983; Steffen, 1984). Butterworths Medical Dictionary (MacNalty, 1965) now defines Marjolin's ulcer as any cancer arising in association with a chronic sinus, ulcer or scar.

A burn scar is a scar that naturally occurs as the healing process of the skin begins shortly after injury.
In some cases there may be particulars of allergenic fibers or traces of irritant chemicals which may become encased within the scab.
This is a probable case scenario for developing carcinoma which is a tumor within the skin and in many times may be malignant.

See below for more:

car路ci路no路ma (plural car路ci路no路mas)
noun
Definitions:
malignant tumor: a malignant tumor that starts in the surface layer epithelium of an organ or body part and may spread to other parts of the body
[Early 18th century. Via Latin < Greek karkin艒ma < karkinos "crab"; from the pattern of the surrounding blood vessels]