FIGURE1.1 Subacute spongiotic dermatitis. Epidermal parakeratosis acanthosis, intraepidermal intercellular edema (spongiosis), and lymphocytic exocytosis. A perivascular lymphocytic inflammatory infiltrate with occasional eosinophils is present in the superficial dermis FIGURE1.2 Lichen simplex chronicus. Orthokeratosis and hypergranulosis with marked irregular acanthosis with minimal spongiosis. The underlying dermis is fibrotic FIGURE1.3 Pityriasis rosea. Focally mounded epidermal parakeratosis, mild spongiosis, and a perivascular lymphocytic inflammatory infiltrate in the papillary dermis FIGURE1.4 Dermatophytosis. Numerous fungal hyphae are present in the stratum corneum in a section stained with periodic acid-Schiff FIGURE1.5 Psoriasis vulgaris. Epidermal parakeratosis with intracorneal neutrophils, hypogranulosis, and regular psoriasiform acanthosis with suprapapillary plate thinning. Vascularity is increased in the dermal papillae. A perivascular lymphocytic inflammatory infiltrate is present in the papillary dermis FIGURE1.6 Pityriasis rubra pilaris. Admixed epidermal orthokeratosis and parakeratosis and psoriasiform acanthosis FIGURE1.7 Lichen planus. Epidermal hypergranulosis, lichenoid interface alteration with "sawtooth" remodeling of the basement membrane zone. A superficial, dense, bandlike lymphocytic inflammatory infiltrate closely approximating the epidermis is present in the dermis FIGURE1.8 Lichen nitidus. The epidermis has a "clawlike" configuration with elongated rete. A delineated, lymphohistiocytic inflammatory infiltrate is present in the papillary dermal papilla FIGURE1.9 Lichenoid drug eruption. Epidermal interface alteration and eosinophils in the inflammatory infiltrate provide a clue to the diagnosis of this type of lichenoid interface dermatitis. Epidermal parakeratosis is typically present FIGURE1.10 Discoid lupus erythematosus. (A) Vacuolar epidermal interface alteration is present at the dermal-epidermal junction. A mild lymphocytic inflammatory infiltrate with admixed melanophages is present in the papillary dermis. (B) Increased interstitial dermal mucin in the reticular dermis FIGURE1.11 Pityriasis lichenoides et varioliformis acuta. Sharply demarcated epidermal parakeratosis, spongiosis, vacuolar interface alteration with epidermal necrosis, and lymphocytic exocytosis. A superficial dermal lymphocytic inflammatory infiltrate FIGURE1.12 Lymphomatoid papulosis. (A) A dense dermal lymphocytic infiltrate The epidermal and dermal alterations often resemble pityriasis lichenoides et varioliformis acuta or pityriasis lichenoides chronica. (B) Under higher magnification, large, atypical lymphocytes with irregularly shaped nuclei are seen These atypical lymphocytes are CD30-positive and closely resemble atypical lymphocytes in cutaneous lymphomas FIGURE1.13 Acute graft-versus-host disease. Vacuolar epidermal interface alteration with dyskeratotic keratinocytes and a sparse lymphocytic inflammatory infiltrate FIGURE1.14 Secondary syphilis. (A) Irregular psoriasiform epidermal changes and a lichenoid mixed inflammatory infiltrate with prominent exocytosis, plasma cells, and focal vacuolar epidermal interface alteration. (B) Treponemal immunohistochemistry demonstrates spirochete organisms in the epidermis FIGURE1.15 Fixed drug eruption. Focal vacuolar epidermal interface alteration and a perivascular lymphocytic inflammatory infiltrate. Eosinophils and melanophages are typically present in the papillary dermis FIGURE1.16 Erythema multiforme. Prominent vacuolar epidermal interface alteration with associated dyskeratotic keratinocytes and a sparse to mild lymphocytic inflammatory infiltrate FIGURE1.17 Toxic epidermal necrosis. Extensive vacuolar epidermal interface alteration with epidermal necrosis and subepidermal blister. A sparse lymphocytic inflammatory infiltrate is present in the dermis FIGURE1.18 Subcorneal pustular dermatosis. A unilocular subcorneal aggregate of neutrophils FIGURE1.19 Scabies. Mite body parts in a subcorneal burrow FIGURE1.20 Bullous impetigo. Subcorneal epidermal bulla with acantholysis and neutrophilic inflammatory infiltrate in the blister space FIGURE1.21 Pemphigus foliaceus. A subcorneal epidermal bulla with rare acantholytic keratinocytes and a mixed inflammatory infiltrate with eosinophils in the blister space FIGURE1.22 Pemphigus vulgaris. Suprabasilar epidermal bulla with prominent acantholysis and a mixed dermal inflammatory infiltrate with eosinophils FIGURE1.23 Pemphigus vegetans. An intraepidermal microabscess with abundant eosinophils and rare acantholytic keratinocytes FIGURE1.24 Benign familial pemphigus (Hailey-Hailey disease). Prominent epidermal acantholysis with suprabasilar clefting FIGURE1.25 Keratosis follicularis (Darier disease). Suprabasal acantholysis with associated dyskeratosis and parakeratosis (grains and corps ronds) FIGURE1.26 Transient acantholytic dermatosis (Grover disease). Suprabasal epidermal acantholysis with focal dyskeratosis and parakeratosis. Grover disease can resemble Darier disease, benign familial pemphigus, and pemphigus vulgaris FIGURE1.27 Herpesvirus infection. Acantholytic keratinocytes with multinucleation, nuclear molding, and nuclear chromatin margination FIGURE1.28 Bullous pemphigoid. A subepidermal bulla with a mixed inflammatory infiltrate containing scattered eosinophils FIGURE1.29 Dermatitis herpetiformis. Neutrophilic microabscesses in the papillary dermal papilla FIGURE1.30 Epidermolysis bullosa. A noninflammatory subepidermal bulla overlies a papillary dermal scar FIGURE1.31 Porphyria cutanea tarda. Subepidermal bulla with minimal inflammation. The dermal papillae protrude into the bulla cavity in the characteristic "festooned" pattern FIGURE1.32 Epidermolytic hyperkeratosis. Epidermal hyperkeratosis with a prominent granular layer characterized by perinuclear clearing and irregular keratohyalin granules (epidermolysis) FIGURE1.33 Ichthyosis vulgaris. Hyperorthokeratotic epidermal hyperkeratosis and a diminished granular layer FIGURE1.34 Acanthosis nigricans. Orthokeratotic hyperkeratosis and regular flat-topped papillomatosis FIGURE1.35 Polymorphous light eruption. Prominent papillary dermal edema with associated epidermal spongiosis and a lymphocytic inflammatory infiltrate FIGURE1.36 Gyrate erythema (erythema annulare centrifugum). Superficial perivascular lymphocytic inflammatory infiltrate closely approximating dermal blood FIGURE1.37 Arthropod bite reaction. Dense, perivascular lymphocytic inflammatory infiltrate with eosinophils FIGURE1.38 Urticaria. A sparse, mixed inflammatory infiltrate with scattered eosinophils in the superficial dermis and mild epidermal spongiosis FIGURE1.39 Pigmented purpura. Superficial perivascular lymphocytic inflammatory infiltrate with extravasated erythrocytes in the papillary dermis FIGURE1.40 Leukocytoclastic vasculitis. Neutrophils with karyorrhexis and evolving fibrinoid necrosis of the vascular wall FIGURE1.41 Acute febrile neutrophilic dermatosis (Sweet syndrome). A diffuse neutrophilic inflammatory infiltrate in the superficial and mid reticular dermis and an intraepidermal pustule FIGURE1.42 Руoderma gangrenosum. (A) A dense dermal neutrophilic inflammatory infiltrate in the dermis. (B) Intact and karyorrhectic neutrophils FIGURE1.43 Urticaria pigmentosa (mastocytosis). A diffuse infiltrate of mast cells is present in the papillary and upper reticular dermis FIGURE1.44 Xanthoma. A diffuse infiltrate of foamy macrophages (xanthoma cells) in the superficial and mid dermis FIGURE1.45 Sarcoidosis. A circumscribed, nonnecrotizing granuloma with a mild associated lymphocytic inflammatory infiltrate FIGURE1.46 Infectious granuloma (cryptococcosis). (A) Numerous fungal yeasts are present in the inflammatory infiltrate. (B) Cryptococcal yeast forms (mucicarmine stain) FIGURE1.47 Foreign body granuloma (Monsel solution reaction). Pigmented histiocytes with golden brown pigment (ferric subsulfate) are present in the papillary and superficial reticular dermis. The iron pigment stains bright blue with special stains such as Perls Prussian blue FIGURE1.48 Granuloma annulare. Necrobiotic granuloma characterized by histiocytes and lymphocytes in a palisaded arrangement around altered collagen fibers and increased dermal mucin FIGURE1.49 Necrobiosis lipoidica. Altered collagen is present between infiltrates of histiocytes, lymphocytes, and plasma cells in a lamellar arrangement ("sandwich" sign) FIGURE1.50 Rheumatoid nodule. A large nodule of fibrinoid, eosinophilic collagen within the deep dermis is surrounded by histiocytes and lymphocytes in a palisaded arrangement FIGURE1.51 Eosinophilic folliculitis. Follicular epithelial spongiosis with an eosinophilic inflammatory infiltrate FIGURE1.52 Alopecia mucinosa. (A) Basophilic mucin deposition within follicular epithelium. (B) Colloidal iron stain highlights the increased intrafollicular mucin FIGURE1.53 Chondrodermatitis nodularis. Epidermal hyperkeratosis, acanthosis and subjacent fibrinoid changes in the dermis. Granulation tissue in the dermis at the periphery of the lesion FIGURE1.54 Keloid. Extensive dermal fibrosis containing characteristic thickened, eosinophilic collagen fibers FIGURE1.55 Morphea/scleroderma. Diffuse dermal sclerosis and absent adnexal structures in late-stage morphea and scleroderma FIGURE1.56 Lichen sclerosus et atrophicus. Hyperkeratosis, epidermal atrophy and extensive sclerosis of the papillary dermal collagen. Focal vacuolar epidermal interface alteration is present FIGURE1.57 Pretibial myxedema. Abundant mucin deposition in the dermis FIGURE1.58 Scleromyxedema. Dermal fibrosis with mild interstitial dermal mucin deposition FIGURE1.59 Cutaneous amyloidosis. (A) Amyloid deposits consisting of amorphous, faintly eosinophilic, acellular material in the superficial dermis. (B) The amyloid deposits show apple green dichroism in Congo red-stained sections under examination with polarized light FIGURE1.60 Calcinosis cutis. Calcium deposits are deeply basophilic in hematoxylin and eosin-stained sections FIGURE1.61 Calciphylaxis. Subcutaneous blood vessel with calcium deposition The vascular calcium deposits can be associated with luminal occlusion by thrombi FIGURE1.62 Erythema nodosum. An expanded, fibrotic subcutaneous septum with a mixed inflammatory infiltrate including neutrophils and multinucleated histiocytic giant cells FIGURE1.63 a₁-Antitrypsin deficiency panniculitis. A neutrophilic panniculitis that involves both lobules (as shown) and septa. Necrosis is typical FIGURE1.64 Pancreatic fat necrosis.Adipocyte basophilia and small calcifications FIGURE1.65 Lupus panniculitis. (A) Delineated, lobular lymphocytic inflammatory infiltrates. Plasma cells are typically admixed in the lymphocytic infiltrates. (B) Hyalinized adipocytic lobules
