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 to 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 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 atopic 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.

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.

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