Clinical Evaluation of 80 Patients with Solar Keratosis Vs 43 Patients with Squamous Cell Carcinoma of Lower Lips: Basal Cell Carcinoma is a Commonly Associated Disease with no Causal Relation

Abstract

Background
Solar keratosis, also known as actinic keratosis or senile keratosis, is a skin condition that results from repeated sun exposure and damage, particularly in middle-aged and elderly individuals. It is characterized by rough, scaly, and warty lesions that may be pigmented, erythematous, or both, and can occur as macules, patches, or plaques. Solar keratosis lesions are most commonly found on the face and scalp and can be associated with basal cell carcinoma but not squamous cell carcinoma or solar keratosis of the lower lip. It is more prevalent in fair-skinned individuals who live in areas with high UV radiation, particularly those over 40 years of age.

Objective
The aim of this study was to document all instances of solar keratosis in patients with Fitzpatrick skin types III and IV, using a comprehensive clinical evaluation. Patients with xeroderma pigmentosum were excluded from the study. The study was conducted between 2014-2021 and involved 80 patients with solar keratosis and 43 patients with squamous cell carcinoma of the lower lips. Demographic information, complete medical history, and clinical evaluations were collected, and biopsies were performed on select patients for histopathological confirmation. This was a cross-sectional descriptive study.

Results
The study included 80 patients with solar keratosis, with ages ranging from 50 to 65 years and a mean age of 58 years. Of these patients, 41 (51.3%) were male and 39 (48.7%) were female. The lesions were predominantly located on the face, affecting 58 (72.5%) patients, while 12 (15%) patients had lesions on both the face and scalp, 4 (5%) had lesions on the scalp, forearms, and hands, and 2 (2.5%) had lesions on the eye sclera. Multiple lesions were present in 62 (77.5%) cases, and a butterfly-shaped distribution on the cheeks was observed in 18 (22.5%) patients (8 females and 10 males). The study identified rough, scaly, warty, and pigmented-erythematous rashes in the form of macules, patches, and plaques as the most common characteristics of the solar keratosis lesions. Among the 80 patients with solar keratosis, only 4 (5%) had the condition on their lower lip, and none of them had squamous cell carcinoma. In contrast, basal cell carcinoma was observed in 50 (62.5%) of patients affecting both faces and scalps, but no squamous cell carcinoma was detected. Among the 43 patients with squamous cell carcinoma of the lower lips, 2 (4.65%) had associated solar keratosis of the face. The age range of the patients with squamous cell carcinoma was 20-78 years, with a mean of 50 years, and the majority (83.7%) were males.

Conclusions
Solar keratosis is a common condition affecting the face and scalp of elderly patients of both sexes, and is often found in conjunction with basal cell carcinoma but not squamous cell carcinoma. This association between solar keratosis and basal cell carcinoma is coincidental rather than causal, as both are common conditions that often occur together. Importantly, solar keratosis of the face does not transform into basal cell carcinoma. Conversely, squamous cell carcinoma of the lower lip is predominantly a disease of males and is not associated with either solar keratosis or cancers of the face.