## 1 Introduction  
The skin is the largest organ in the body; it covers and protects externally. Its condition and appearance show the state of health and wellbeing of a person; however, due to exposure to the environment and other factors, specific skin injuries may occur; these can vary in size and shape. Different types of skin diseases vary according to the symptoms. The presence of any mild skin condition can lead to severe complications and even death. Skin cancer is a serious disease and one of the most common carcinomas. It is mainly classified into basal cell carcinoma (BCC), squamous cell carcinoma or epidermoid carcinoma (SCC), and melanoma (MEL) [1; 2; 3; 4]. BCC is the most frequent skin cancer in the worldwide population, and its growth is slow. It can grow and destroy the skin. It is generally observed as a flat or raised lesion and its color is reddish [1; 5; 6; 7]. SCC is a malignant tumor that appears as red spots with raised growths like warts; it is the second most common skin cancer [1; 2]. Melanoma is the most aggressive skin cancer, appearing as a pigmentedlesion, usually beginning on normal skin as a new, small, pigmented growth [2]. Other common skin diseases are actinic keratosis (AK), benign keratosis (BKL), dermatofibromas (DF), melanocytic nevi (NV), and vascular lesions (VASCs), among others. Actinic keratosis occurs due to frequent exposure to ultraviolet rays from the sun or tanning beds; it usually appears as small rough spots and presents color variations. Some areas are generally malignant, causing squamous cell carcinoma [7; 8; 9]. Seborrheic keratoses or benign keratoses are benign tumors that frequently occur in the geriatric population. This type of tumor consists of a brown, black, or light brown spot or lesion. In some cases, it is often confused with basal cell carcinoma or melanoma [10; 11]. Dermatofibroma is a benign skin lesion; it appears as a slow-growing papule, and its color varies from light to dark brown, purple to red, or yellowish. Its clinical diagnosis is simple; however, sometimes it is difficult to differentiate it from other tumors, such as malignant melanoma [12; 13]. Melanocytic nevi or moles are the most common benign lesions and have smooth, flat, or palpable surfaces. They form as a brown spot or freckle that varies in size and thickness [14; 15]. Vascular lesions are disorders of the blood vessels. They become evident on the skin's surface, forming red structures, dark spots, or scars, presenting an aesthetic problem. Some VASCs develop over time due to environmental changes, temperature, poor blood circulation, or sensitive skin [16; 17]. The skin can warn of a health problem; its care is critical for physical and emotional aspects. Different conditions can affect the skin; some are present at birth, whereas others are acquired throughout life. Some lesions may have similar characteristics, making it difficult to differentiate them from the most common malignant neoplasms. Skin diseases are a significant health problem. The development of new digital tools and technologies based on artificial intelligence (AI) to detect and treat diseases is due to the ability to analyze large amounts of data. The latest developments based on artificial intelligence tools help identify health problems in the early stages. These developments are also based on image processing, where the recognition of visual patterns through images represents a potential solution for the failure of the human eye to detect disease. Applying algorithms based on artificial intelligence allows the development of non-invasive tools in the health area. In recent decades, machine learning (ML) techniques have been used in impressive applications in many research areas and are still growing. Since many studies about medical imaging are focused on automating skin lesion identification from dermatological images to provide an adequate diagnosis and treatment to patients, ML techniques can be a powerful tool to detect malignant lesions automatically, quickly, and reliably.