Types of benign naevi and pigmented lesions Melanocytic Naevus Common benign skin lesions due to a local proliferation of pigment cells -> melanocytes. Can be present at birth or acquired later in life. Vary widely in colour, shape and size. Blue Naevus Harmless mole with a dark blue colour. Halo Naevus Mole surrounded by a pale ring -> compared to surrounding structures. May gradually go away by itself. Dysplastic or atypical naevi Multiple with irregular pigmentation and shape. Tent to run in some families. Have a greater tendency to transform into melanoma compared to most moles. Clinical and pathological differences between benign, premalignant and malignant pigmented lesions. Benign Pigmented Lesions Clinical Features Appearance: Benign lesions, such as moles (melanocytic naevi), tend to have distinct borders and can vary in colour from pink or flesh tones to dark brown, blue, or black. Growth: They typically grow slowly and remain localized in their primary location without invading other tissues. Symptoms: Benign lesions are usually asymptomatic but can become problematic if they compress nearby structures (e.g., causing pain or difficulty breathing). Pathological Characteristics Cell Behaviour: Benign tumours consist of cells that divide at a normal rate and maintain their differentiated state. Invasion: They do not invade surrounding tissues or spread to distant sites. Recurrence: Once removed, benign lesions are unlikely to recur. Examples: Fibroids in the uterus and lipomas in the skin are common examples of benign tumours. Premalignant (Precancerous) Pigmented Lesions Clinical Features Appearance: Premalignant lesions may appear similar to benign ones but carry a higher risk of transformation into malignancy. Monitoring: Close surveillance is necessary to detect any progression. Pathological Characteristics Cell Behaviour: Cells in premalignant lesions exhibit some abnormal features but are not yet fully cancerous. Risk of Transformation: These lesions have the potential to become malignant over time. Examples: Actinic keratoses (scaly patches on sun-exposed skin) and some types of dysplastic nevi fall into this category. Malignant Pigmented Lesions (Cancer) Clinical Features Appearance: Malignant lesions can be similar in appearance to benign or premalignant ones but often exhibit rapid growth and irregular borders. Spread: They invade surrounding tissues and can metastasize to distant sites via the bloodstream or lymphatic system. Symptoms: Depending on the location, symptoms may include pain, bleeding, or changes in texture. Pathological Characteristics Cell Behaviour: Malignant tumours consist of cells that grow uncontrollably, lose differentiation, and invade adjacent tissues. Metastasis: Spread to distant organs (metastasis) is a hallmark of malignancy. Treatment: Early-stage malignant lesions are often treated with surgery, chemotherapy, or radiotherapy. Advanced cases require systemic treatments like immunotherapy or targeted therapy. Examples: Melanoma (a type of skin cancer) and other malignant skin tumours fall into this category.