1 What's new in the fifth edition¿ 2 An approach to the interpretation of skin biopsies¿ 3 Diagnostic clues¿ 4 The lichenoid reaction pattern ("interface dermatitis")¿ 5 The psoriasiform reaction pattern¿ 6 The spongiotic reaction pattern¿ 7 The vesiculobullous reaction pattern¿ 8 The granulomatous reaction pattern¿ 9 The vasculopathic reaction pattern 10 Disorders of epidermal maturation and keratinization¿ 11 Disorders of pigmentation¿ 12 Disorders of collagen¿ 13 Disorders of elastic tissue 14 Cutaneous mucinoses 15 Cutaneous deposits 16 Diseases of cutaneous appendages 17 Cysts, sinuses, and pits 18 Panniculitis 19 Metabolic and storage diseases 20 Miscellaneous conditions 21 Cutaneous drug reactions¿ 22 Reactions to physical agents 23 Cutaneous infections and infestations-histological patterns¿ 24 Bacterial and rickettsial infections¿ 25 Spirochetal infections¿ 26 Mycoses and algal infections¿ 27 Viral diseases¿ 28 Protozoal infections¿ 29 Marine injuries¿ 30 Helminth infestations¿ 31 Arthropod-induced diseases¿ 32 Tumors of the epidermis¿ 33 Lentigines, nevi, and melanomas¿ 34 Tumors of cutaneous appendages¿ 35 Tumors and tumor-like proliferations of fibrous and related tissues 36 Tumors of fat 37 Tumors of muscle, cartilage, and bone 38 Neural and neuroendocrine tumors 39 Vascular tumors 40 Cutaneous metastases 41 Cutaneous infiltrates-nonlymphoid 42 Cutaneous infiltrates-lymphomatous and leukemic