INTRODUCTION: The advent of squamous cell carcinomas (SCC) from chronic dermatoses is known but little explored. Although rare, tumors originating there have a worse prognosis, in part due to late diagnosis.
OBJECTIVES: This study aims to survey cases of squamous cell carcinoma developed on previous dermatoses diagnosed between 2000 and 2020 in a tertiary health service.
METHODS: This is a quantitative and retrospective study through biopsy reports survey and medical records review.
RESULTS: From an initial list of 11,249 histological reports compatible with squamous cell carcinoma, we obtained a final list of 10 patients. The study findings corroborate the literature regarding some known risk factors: abundant and chronic sun exposure, older than 50 years, lower skin phototypes, and immunosuppression. We also found a high frequency of smoking and lichenoid dermatoses (5/10 patients) in the studied population, including chronic cutaneous lupus erythematosus and hypertrophic lichen planus.
CONCLUSIONS: It is not possible to predict the primary risk factors for the development of squamous cell carcinomas regarding previous dermatoses, although there is a tendency for their appearance in lichenoid dermatoses and those with longer evolution.

Keywords: Skin diseases; Squamous cell carcinoma; Lupus erythematosus, Cutaneous; Lichen planus