Introduction to Dermatology and Dermatopathology Anthony A. Gaspari, M.D.

Functions of the Skin

Primary

• Protection against physical injury, wear and tear-sensory function
• Impermeability to passage of chemicals, including water from outside or within
• Resistance to microbial penetration

Secondary

• Protection against ultraviolet injury
• Thermoregulation
• Endocrine functions
• Communication

Structural Adaptions of the Skin to Subserve Its Functions

• Hair
• Nails
• Eccrine sweat glands
• Apocrine glands
• Sebaceous glands

Cellular and Biochemical Components of Skin

Macroscopic Terminology

Clinical Correlations of Pathology

	Macule Flat area of color change Generally due to pigmentary changes: melanin, oxyhemoglobin, carotene, hemosiderin or foreign substances (drug deposition, tattoo) Examples: lentigo maligna, nevus, drug deposition
	Papule Elevated lesion <5 mm Correlation: space occupation by cells, either inflammatory or tumor Examples: lichen planus, dermatofibroma
	Nodule, Tumor Elevated lesion > 5 mm Correlation: Larger, often deeper allowing skin to move over the surface (iceberg phenomena) Examples: basal cell carcinoma, hemangioma
	Plaque Broad-based elevated lesion, diameter greater than height Correlation: histologically not distinguished from papule or nodule Example: psoriasis
	Wheal Transient swelling without secondary changes Correlation: caused by edema in upper dermis Examples: urticaria, dermatographism
	Vesicle Fluid filled lesion <1 cm within or beneath the epidermis Examples: poison ivy
	Bulla Fluid filled lesion> 1 cm Example: pemphigus vulgaris
	Cyst Circumscribed tumor containing semi-solid or liquid material Example: epidermoid cyst
	Pustule Focal accumulation of neutrophils (or eosinophils) and serum Example: pustular psoriasis
	Purpura Leakage of blood into the skin Example: Kaposi's sarcoma
Secondary Changes - secondary changes tend to be less specific
	Scale - flaking from the epidermis Example: Psoriasis
	Crust Collection of inflammatory cells and serum on the surface Example: poison ivy
	Excoriation Loss of epidermis induced specifically by scratching Example: poison ivy
	Fissure Split in epidermis extending to the dermis Example: Atopic eczema
	Lichenification Exaggeration of skin markings, secondary to chronic itching Example: atopic eczema
	Erosion Loss of epidermis, dermis intact, heals without scarring Example: Pemphigus
	Ulcer Loss of epidermis and at least part of the dermis, healing usually results in scarring Example: Squamous cell carcinoma
	Atrophy Loss of substance of skin. Can be epidermal, dermal or subcutaneous Example: lipodystrophy