Abscess – a closed pocket filled with pus. These may be painful and pus can be visible, or they stay closed and appear much like tumors, requiring a biopsy.

Acne – a skin disorder involving pores and hair follicles, acne can appear as blackheads, pimples, scarring and other skin-related problems.

Angioma – a benign skin tumor, usually consisting of lymph vessels and blood.

Bullous – a large blister-like sac of fluid appearing on the skin.

Biopsy – the process of medically examining tissue microscopically, usually to discover what type of tissue it is, or determine its behavior.

Blister – any pocket of bodily fluid on the skin.

Boil – swollen and sore areas of the skin that appear around hair follicles.

Carcinoma – a malignant cancer deriving from the skin. Some types include basal and squamous cell carcinomas.

Carbuncles – a cluster of boils.

Collagen – a protein produced by the skin that gives it elasticity and strength.

Congenital – present at birth.

Cyst – a deep lesion filled with pus, blood or another fluid.

Dermatitis – a skin condition marked by skin inflammation.

Dermis – the middle layer of skin, between the subcutis and epidermis.

Eczema – also called dermatitis, eczema is marked by itching, scaling and thickening skin, usually around the face, elbows or knees.

Epidermis – the topmost layer of skin, above the dermis.

Hives – raised, red, itchy patches on the skin, usually caused by allergies to a food or medicine. Also called urticaria.

Inflammation – redness, pain and heat in the skin.

Lentigines – dark areas of the skin caused by sun exposure. Also called age spots, liver spots or sun spots.

Lesion – areas of discoloration or inflammation, often caused by, or indicative of, tumors.

Melanin – the pigment that gives our skin color.

Melanocytes – cells that produce and distribute melanin to the skin.

Moles – raised dark areas in the skin caused by the damage or dysfunction of melanocytes.

Polyp – benign skin structures with a mushroom-like form of a head attached to a stalk. Also called skin tags.

Psoriasis – a skin condition where itchy, red marks on the body produce silvery scales.

Rosacea – a common skin condition affecting the face, usually consisting of acute redness, broken and dilated blood vessels, and pimples.

Subcutis – the innermost layer of skin, beneath the dermis.

Tumor – a lump which can be seen or felt. While they are often associated with cancer, not all tumors are cancerous, and not all cancers involve tumors.