RESUMEN
INTRODUCTION: Several disparate mucocutaneous diseases present oral mucosal lesions that have been classically labeled as "pre-cancerous", "pre-malignant", or "potentially malignant". These include oral lichen planus, dyskeratosis congenita, tertiary syphilitic glossitis chronic graft-versus-host-disease, and oral discoid lupus erythematosus. There is much confusion in literature regarding the real malignant potential of these oral lesions in relation to the incidence of squamous cell carcinoma. OBJECTIVES: We tried to unify the occurrence of squamous cell carcinoma in some oral mucosal diseases into the classic concept of "Marjolin ulcer". METHODS: We analyzed the most relevant published evidence of the occurrence of squamous cell carcinoma arising in oral lichen planus, dyskeratosis congenita, tertiary syphilitic glossitis chronic graft-versus-host-disease, and oral discoid lupus erythematosus, and tried to establish a logical link between them. RESULTS: Reported cases of squamous cell carcinoma occurring in oral lesions of these diseases seem to appear in old standing, scarring lesions. CONCLUSIONS: Oral lichen planus, dyskeratosis congenita, tertiary syphilitic glossitis, chronic graft-versushost-disease, and oral discoid lupus erythematosus are not "pre-malignant diseases", their long-lasting mucosal scars are prone to the development of squamous cell carcinomas. In this sense, this tumor can be considered a mucosal type of Marjolin ulcer.