Günter Burg, MD is Professor of Dermatology and Chairman Emeritus, University of Zurich, Switzerland.

Heinz Kutzner, MD is Professor of Dermatology, Institute of Dermatopathology, Friedrichshafen, Germany,

Werner Kempf, MD is Professor of Dermatology, Department of Dermatopathology, University of Zurich, Switzerland.

Josef Feit, MD is Associate Professor of Pathology, University of Ostrava, Czech Republic.

Bruce R. Smoller, MD is Professor and Chairman of the Department of Pathology and Laboratory Medicine, University of Rochester, NY, School of Medicine and Dentistry.

Preface xv

Acknowledgments xvii

1 EPIDERMIS 1

Nevi 2

Epidermal Nevus 2

Variant: Inflammatory Linear Verrucous Epidermal Nevus (ILVEN) 3

Keratoses 4

Seborrheic Keratosis (SK) and Variants 4

Variant: Acanthotic Seborrheic Keratosis 4

Variant: Reticulated, Pigmented Seborrheic Keratosis 6

Variant: Flat Seborrheic Keratosis 6

Variant: Papillomatous Seborrheic Keratosis 7

Variant: Activated (Irritated) Seborrheic Keratosis 7

Variant: Dermatosis Papulosa Nigra 7

Variant: Melanoacanthoma (Pigmented Seborrheic Keratosis) 8

Variant: Clonal (Intraepidermal) Seborrheic Keratosis (Borst- Jadassohn) 9

Variant: Seborrheic Keratosis with Monster Cells (Bowenoid) 10

Variant: Hyperkeratotic Seborrheic Keratosis (Stucco Keratosis) 11

Confluent and Reticulate Papillomatosis (Gougerot and Carteaud) 12

Reticulate Pigmented Anomaly of the Flexures (Dowling-Degos Disease) 13

Acanthosis Nigricans 14

Solar (Actinic) Keratosis 15

Variant: Acantholytic Solar Keratosis 16

Variant: Atrophic Solar Keratosis 16

Variant: Lichen Planus-Like Solar Keratosis 17

Variant: Hypertrophic (Bowenoid) Solar Keratosis 18

Cornu Cutaneum 18

Acanthomas, Non-Viral 19

Solar Lentigo 19

Callus, Factitial Acanthoma 20

Knuckle Pads (Chewing Pads) 21

Pale (Clear) Cell Acanthoma 22

Large Cell Acanthoma 23

Differential Diagnosis: Epidermolytic Acanthoma 24

Differential Diagnosis: Congenital Ichthyosiform Erythroderma 25

Acantholytic Acanthoma 26

Warty Dyskeratoma 27

Porokeratoma (Porokeratosis Mibelli) 30

Acanthomas, Viral 31

Verruca Vulgaris 31

Variant: Verruca Plana 33

Variant: Condyloma Acuminatum 34

Bowenoid Papulosis 35

Acrokeratosis Verruciformis (Hopf) 37

Molluscum Contagiosum 38

"Pseudocarcinomas" and Neoplasms with Intermediate Malignant Potential 40

Keratoacanthoma (KA) 40

Epithelioma Cuniculatum (Verrucous Carcinoma) (EC/VC) 44

Papillomatosis Cutis Carcinoides 45

Florid Papillomatosis of the Oral Cavity (Oral Verrucous Carcinoma) 46

Buschke-Löwenstein Tumor (Giant Condyloma) 47

Malignant Epidermal Neoplasms 48

Bowen's Disease (Carcinoma in situ) 48

Variant: Clear Cell Bowen's Disease 50

Variant: Cutaneous Horn (Cornu Cutaneum) on Bowen's Disease 51

Variant: Pigmented (Anogenital) and Clonal Bowen's Disease 52

Variant: Erythroplasia of Queyrat and Vulvar Intraepithelial Neoplasia 53

Basal Cell Carcinoma (BCC) 54

Variant: Nodular BCC 54

Variant: Infundibulocystic BCC 56

Variants of BCC With Ductal, Matrical or Sebaceous Differentiation 57

Variant: Superficial BCC 60

Variant: Pigmented BCC 61

Variant: Adenoid-Cystic BCC 62

Variant: Sclerodermiform (Morpheaform) BCC 64

Clinical Variants: Ulcerating BCCs 66

Histological Variants: Metatypic BCC with Squamoid Differentiation 67

Syndromatic BCC (Basal Cell Nevus Syndrome, Gorlin-Goltz) 69

Fibroepithelioma of Pinkus 70

Squamous Cell Carcinoma (SCC) 72

Variant: Well-Differentiated SCC 72

Variant: Acantholytic SCC (Epithelioma Spinocellulare Segregans of Delacretaz) 74

Variant: Myxoid SCC 76

Variant: Follicular (Infundibular) SCC 77

Variant: Spindle Cell (Fusicellular) SCC 78

Squamous Cell Carcinomas in Special Sites 79

2 ADNEXAL 85

Sweat Gland Differentiation 86

Nevi, Hyperplasias, and Benign Adnexal Neoplasms (BAN) 86

Eccrine Differentiation 86

Apocrine Differentiation 93

Malignant Adnexal Neoplasms 105

Eccrine Differentiation 105

Apocrine Differentiation 109

Sebaceous Differentiation 110

Hyperplasias and Hamartomas 111

Ectopic (Heterotopic) Sebaceous Glands (Fordyce Glands) 111

(Senile) Sebaceous Gland Hyperplasia 112

Nevus Sebaceous (Jadassohn) 113

Variant: Pilo-Sebaceous Hamartoma 114

Benign Neoplasms 114

Sebaceous Adenoma 114

Muir-Torre Syndrome 115

Sebaceous Epithelioma (Sebaceoma) 116

Malignant Neoplasms 118

Sebaceous Carcinoma 118

Hair Follicle Differentiation 119

Nevi, Hyperplasia, and Hamartomas 119

Hair Follicle Nevus 119

Conical Infundibular Acanthoma (Giant Dilated Pore of Winer) 120

Benign Neoplasms 121

Pilar Sheath Acanthoma 121

Trichilemmoma (Tricholemmoma) 122

Tumor of the Follicular Infundibulum (Infundibuloma) 124

Trichoepithelioma (Superficial Trichoblastoma) 125

Trichoblastoma (Trichoblastic Fibroma; Immature Trichoepithelioma) 127

Trichoepithelioma (Sclerosing Epithelial Hamartoma) 131

Trichofolliculoma (Folliculosebaceous Cystic Hamartoma) 133

Trichoadenoma (Nikolowski) 136

Pilomatricoma (Calcifying Epithelioma Malherbe) 137

Proliferating Trichilemmal (Pilar) Tumor (PTT) (Proliferating Trichilemmal Cyst) 138

Malignant Neoplasms 140

Malignant Pilomatricoma (Pilomatrical Carcinoma) 140

Trichilemmal Carcinoma 141

Trichoblastic Carcinoma 142

Pilosebaceous Mesenchyme 143

Benign Neoplasm 143

Trichodiscoma (Follicular Fibroma, Fibrofolliculoma, Perifollicular Fibroma) 143

3 PAGET'S DISEASE 145

Mammary Paget's Disease 146

Extramammary Paget's Disease 146

4 MELANOCYTES 149

Non-Neoplastic Hyperpigmentations 150

Ephelides (Genuine Freckles) 150

PUVA (Psoralen UVA) Lentigo 150

"Nevus" Spilus (Speckled Lentiginous Nevus; Café-Au-Lait Spot) 151

"Ink" Spot Lentigo (Reticulated Melanocytic Macule) 152

Senile Freckles (Solar [Actinic] Lentigo) 153

Mucosal Lentiginous Spots (Lip, Buccal, and Genital Mucosa) 154

Nevi 155

Common Acquired Melanocytic Nevi 155

Melanosis Neviformis (Pigmented Hairy Epidermal Nevus; Becker Nevus) 155

Junctional Nevus 156

Compound Nevus 157

Dermal Nevus 158

Variant: Miescher's Nevus (Dermal Nevus) 160

Variant: Balloon Cell Nevus 161

Variant: "Activated" Acral (Lentiginous) Melanocytic Nevus 161

Variant: (Atypical) Genital Melanocytic Nevus 162

Variant: Halo Nevus (Leukoderma Centrifugum Acquisitum; Sutton Nevus) 163

Variant: Eczematoid Melanocytic (Meyerson's) Nevus 165

Variant: Osteo-Nevus of Nanta 166

Variant: Combined Epithelioid Spitzoid Nevus, "Wiesner Nevus" (BAP-1 Deficient Epithelioid Melanocytic Tumor) 167

Variant: Recurrent (Persistent) Melanocytic Nevus (Pseudomelanoma) 167

Variant: Nevus in Pregnancy 168

Variant: Ancient Nevus 170

Blue Nevi 171

Common Blue Nevus 171

Common Blue Nevus 172

Dermal Melanocytosis 177

Nevus Fuscoceruleus (Ota; Ito; Mongolian Spot) 177

Spindle and/or Epithelioid Cell Nevus 178

Common Nevus of Spitz 178

Variants of Spindle and Epithelioid Cell Nevus 179

Variant: Pigmented Spindle Cell Nevus (Reed) 182

Benign Melanocytic Lesions with Peculiar Structural Features 183

Melanocytic Nevus with Clonal Proliferation 183

Atypical (Dysplastic) Melanocytic (Clark's) Nevus (B-K Mole Syndrome) 185

Congenital Nevi, Small and Medium-Sized (1.5-20 cm) 186

Malignant Melanocytic Neoplasms 188

Lentigo Maligna Dubreuilh (Hutchinson's Freckle) 188

Malignant Melanoma 189

Variant: Superficial Spreading Melanoma (SSM) 190

Variant: Lentigo Maligna Melanoma (LMM) 192

Variant: Nodular Melanoma (NM) 193

Variant: Acral Lentiginous Melanoma (ALM) 194

Variant: Melanoma in Large Congenital Melanocytic Nevus (LCMN) 196

Variant: Cutaneous Metastasis of Melanoma 197

Special Localisations of Malignant Melanoma 204

Tumor Thickness and Levels 205

Common Clinical Differential Diagnoses of Malignant Melanoma 205

5 CONNECTIVE TISSUE 207

Nevi 208

Connective Tissue Nevus (Shagreen Patch; Cobblestone Nevus; Nevus Collagenicus) 208

Fibrous Neoplasms 209

Soft Fibroma (Skin Tag; Acrochordon) 209

Perifollicular Fibroma (Fibrofolliculoma; Trichodiscoma) 210

Variant: Sclerotic Fibroma (Plywood Fibroma; Storiform Collagenoma) 211

Variant: Fibrous Papule of the Nose 212

Variant: Pleomorphic Sclerosing Fibroma with Multinucleated Cells 212

Keloid 213

Infantile Digital Fibromatosis (Inclusion Body Fibromatosis; Recurring Digital Fibrous Tumor of Children; Reye's Tumor) 214

Malformations with Supernumerary Tissue Elements 216

Supernumerary Digit (Rudimentary Digit; Rudimentary Polydactyly) 216

Differential Diagnosis: Acral Acquired Fibrokeratoma 216

Accessory Tragus (Preauricular Tag) 217

Accessory Nipple (Ectopic Breast; Polythelia) 218

Fibrohistiocytic Neoplasms 218

Dermatofibroma (Benign Fibrous Histiocytoma; Fibroma Durum; Sclerosing Hemangioma) 218

Dermatofibrosarcoma Protuberans 227

Variant: Pigmented Dermatofibrosarcoma Protuberans (Bednar's Tumor) 230

Variant: Giant Cell Fibroblastoma 231

Pleomorphic Dermal Sarcoma (PDS) 231

Miscellaneous Tumors 234

Epithelioid Sarcoma 234

Dermatomyofibroma 236

6 VESSELS 239

Hamartomas, Nevi, and Malformations 240

Phacomatosis Pigmentovascularis 240

Eccrine Angiomatous Hamartoma 241

Nevus Anemicus 242

Capillary Malformations 242

Nevus Flammeus (Port-Wine Stain) 242

Nevus Araneus (Spider Angioma) 244

Cutis Marmorata Telangiectatica (van Lohuizen) (Nevus Vascularis Reticularis) 245

Congenital Telangiectatic Erythema (Bloom's Syndrome) 247

Venous Malformations 248

Blue Rubber Bleb Nevus Syndrome (Familial Venous Malformation) 248

Hereditary Hemorrhagic Telangiectasia (Osler-Weber-Rendu) 249

Angioma Serpiginosum 250

Venular Aneurysm (Venous Lake) 251

Cavernous Hemangioma (in Maffucci Syndrome) 252

Sinusoidal Hemangioma 253

Spindle Cell Hemangioma (Formerly Spindle Cell Hemangioendothelioma) 254

Arteriovenous Malformations 256

Acral Arteriovenous Hemangioma (Cirsoid Aneurysm) 256

Glomuvenular Malformation ("Glomangioma") 257

Lymphatic Malformations 259

Superficial Lymphatic Malformation (Superficial Lymphangioma) 259

Cystic Lymphatic Malformation (Cystic Hygroma) 260

Targetoid Hemosiderotic (Hobnail) Hemangioma 261

Progressive Lymphangioma (Benign Lymphangioendothelioma) 262

Lymphangiomatosis 263

Angiokeratomas 264

Verrucous Hemangioma (Venous Malformation) 265

Variant: Solitary Angiokeratoma 268

Variant: Angiokeratoma Circumscriptum Naeviformis 269

Variant: Fordyce Angiokeratoma 269

Variant: Angiokeratoma Acroasphycticum Digitorum (Mibelli) 269

Variant: Multiple "Pinpoint" Angiokeratomas (Angiokeratoma Corporis Diffusum; Fabry's Disease) 269

Variant: Acral Pseudolymphomatous Angiokeratoma of Children (APACHE) 269

Hyperplasias...