Atlas of Dermatopathology

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

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

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

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

Bruce R. Smoller, MD, Professor and Chairman of the Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, School of Medicine and Dentistry, Rochester, USA

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 270

Granuloma Pyogenicum (Lobular Capillary Hemangioma; Botryomykoma) 270

Differential Diagnosis: Pyogenic Granuloma‐Like Granulation Tissue 272

Bacillary Angiomatosis 273

Verruga Peruana 274

Intravascular Papillary Endothelial Hyperplasia (Masson) 275

Acroangiodermatitis Mali (Pseudo‑Kaposi’s Sarcoma) 276

Benign Vascular Neoplasms 278

Epithelioid Hemangioma (Angiolymphoid Hyperplasia with Eosinophilia, ALHE) 278

Endothelial Differentiation 280

Infantile Capillary and Congenital Hemangioma 280

Cherry Angioma (Senile Hemangioma) 281

Microvenular (Microcapillary) Hemangioma 282

Tufted Angioma 283

Kaposiform Hemangioendothelioma 285

Glomeruloid Hemangioma in POEMS Syndrome 287

Pericytic Differentiation 288 Imitator: Solitary Fibrous Tumor of the Skin (SFT) 289

Myopericytoma (Infantile Myofibromatosis; Perivascular Myoma (incl. Myofibroma)) 290

Glomoid and Myoid Differentiation 292

Glomus Tumor 292

Angioleiomyoma (Angiomyoma; Vascular Leiomyoma) 294

Recently Described Benign Vascular Tumors 296

Symplastic Hemangioma 296

Papillary Hemangioma 297

Vascular Neoplasms of Intermediate Malignant Potential 298

Kaposi’s Sarcoma (KS) 298

Retiform Hemangioendothelioma 305

Composite Hemangioendothelioma 306

Papillary Intralymphatic Angioendothelioma (PILA) (Malignant Endovascular Papillary Angioendothelioma (Dabska Tumor); Endovascular Papillary Hemangioendothelioma) 306

Radiation‐Induced Atypical Vascular Lesion (AVL) (Benign Lymphangiomatous Papule (BLAP)) 308

Vascular Neoplasms with High Malignant Potential 309

Cutaneous Angiosarcoma 309

Radiation‐Induced (Postradiation) Angiosarcoma 312

Epithelioid Hemangioendothelioma 312

Epithelioid Angiosarcoma 315

Differential Diagnosis: Acantholytic (Angiosarcoma‐Like) Squamous Cell Carcinoma 316

Glomangiosarcoma (Malignant Glomus Tumor) 317

Other Neoplasms with Significant Vascular Component 318

Multinucleate Angiohistiocytoma 318

Angiofibroma (Adenoma Sebaceum Associated with Pringle–Bourneville Disease) 319

Angiolipoma 321

Angiolipoleiomyoma (Angiomyolipoma) 322

Angiomyxoma 322

Intralymphatic Histiocytosis 324

Kimura’s Disease 325

7 FAT 327

Nevus (Hamartoma) 328

Nevus Lipomatosus Superficialis Hoffmann Zurhelle 328

Neoplasms of Fat Tissue 329

Benign Neoplasms 329

Common Lipoma and Lipomatosis 329

Angiolipoma (see Vessels, Chapter 6) 330

Angiomyolipoma (see Vessels, Chapter 6) 330

Spindle Cell Lipoma 330

Pleomorphic Lipoma (see Pleomorphic Liposarcoma) 332

Hibernoma 332

Malignant Neoplasms 333

Cutaneous Liposarcoma 333

8 MUSCLE 337

Benign Neoplasms 338

Piloleiomyoma (Pilar Leiomyoma) 338

Angioleiomyoma (see Vessels, Chapter 6) 340

Rhabdomyoma, Adult Type 340

Malignant Neoplasms 341

Rhabdomyosarcoma 341

Superficial Leiomyosarcoma 342

9 NERVES 345

Benign Neoplasms 346

Schwannoma (Neurilemmoma) 349

Solitary Neuroma (“Palisaded Encapsulated Neuroma”) 352

Variant: Traumatic Neuroma 353

Granular Cell Tumor (Abrikossoff) 354

Dermal Nerve Sheath Myxoma (Myxoid Neurothekeoma) 356

Variant: Cellular Neurothekeoma 357

Pacinian Neurofibroma (Pacinoma) 358

Malignant Neoplasms 358

Malignant Peripheral Nerve Sheath Tumor (Malignant Schwannoma) 358

Malignant Granular Cell Tumor 360

Neuroendocrine Neoplasm 360

Primary Neuroendocrine (Merkel Cell, Trabecular) Carcinoma of the Skin 360

10 MAST CELLS 363

Solitary Cutaneous Mast Cell Proliferation 364

Cutaneous Mastocytoma 364

Diffuse Cutaneous Mast Cell Proliferations 365

Urticaria Pigmentosa (Juvenile Maculopapular Mastocytosis) 365

Telangiectasia Macularis Eruptiva Perstans (Adults) 365

Systemic Mast Cell Proliferation 367

Involvement of Skin and Bone Marrow 367

11 HISTIOCYTES 369

Langerhans Cell Histiocytoses (LCH) 370

Precursors of Langerhans Cell Histiocytoses 370

Congenital Self‐healing Reticulohistiocytosis (Hashimoto–Pritzker) 370

Indeterminate Cell Histiocytosis 371

Langerhans Cell Histiocytoses (Histiocytosis X) 371

Congenital Langerhans Cell Histiocytosis (Letterer–Siwe Disease) 372

Hand–Schüller–Christian Adult LHC Histiocytosis 374

Solitary Langerhans Cell Tumor (Eosinophilic Granuloma) 375

Non‐Langerhans Cell Histiocytoses 376

Proliferative 376

Proliferative Histiocytoma (Progressive Nodular Histiocytosis, PNH) 376

Benign Cephalic Histiocytosis 377

Multicentric Reticulohistiocytosis (Lipoid Dermatoarthritis) (Solitary Reticulohistiocytoma) 378

Sinus Histiocytosis With Massive Lymphadenopathy 379

Granulomatous Storing 380

Juvenile Xanthogranuloma (Nevoxanthoendothelioma; Xanthoma Multiplex; Juvenile Giant Cell Granuloma) 380

Xanthelasma Palpebrarum 383

Verruciform Xanthoma 384

Necrobiotic Xanthogranuloma (with Paraproteinemia) 385

Hereditary Progressive Mucinous Histiocytosis 386

Hemophagocytic 387

Familial Hemophagocytic Lymphohistiocytosis 387

Histiocytic Cytophagic Panniculitis 388

12 HEMATOPOIETIC DISORDERS 389

Lymphoid Skin Infiltrates 389

Cytomorphology, Major Cell Types 390

T‐Cells 390

B‐Cells 391

Pattern of Small Cell Lymphocytic Infiltrates 392

T‐Cell Pattern 392

B‐Cell Pattern 392

Pseudolymphoma (PL) 393

Nodular B‐Cell PL 393

Lymphadenosis Cutis Benigna (Lymphocytoma Cutis) 393

Differentiation between B‑Pseudolymphoma (PL) and Cutaneous B‐Cell Lymphoma (CBCL) 395

Nodular T‐Cell PL 396

CD30+ Pseudolymphoma in Scabies 396

Papular (Secondary) Syphilis 398

Pseudo‐Mycosis Fungoides (Mycosis Fungoides Simulators) 399

Lymphomatoid Contact Dermatitis 399

Lichen Planus 399

Drug Reactions 400

Early Vitiligo 400

Lichen Sclerosus et Atrophicus 400

Pityriasis Lichenoides Chronica 401

Graft Versus Host Reaction (Acute) 401

Pityriasis Lichenoides et Varioliformis Acuta (PLEVA) 402

Pigmented Purpuric Dermatitis (Lichen Aureus) 403

Lymphocytic Infiltration Jessner–Kanof 404

Cutaneous Mature T‐Cell Lymphoid Neoplasms (CTCL) 405

Mycosis Fungoides, Classic Alibert–Bazin Type 405

Mycosis Fungoides Patch Stage I 405

Mycosis Fungoides Plaque Stage II (CD4+; CD8−) 407

Variant: CD8+ Mycosis Fungoides 409

Mycosis Fungoides Tumor Stage III 409

Large Cell Transformation 410

Simulators and Variants of Mycosis Fungoides: “Parapsoriasis” 411

Simulator: Small Plaque Parapsoriasis (SPP) (Brocq’s Disease, Digitate Dermatosis) 411

Large Plaque Parapsoriasis (LPP) 412

Pigmented Purpuric Mycosis Fungoides 412

Erythrodermic Mycosis Fungoides 412

Folliculotropic (Pilotropic) Mycosis Fungoides 413

Syringotropic Mycosis Fungoides (Syringolymphoid Hyperplasia with Alopecia) 414

Granulomatous Mycosis Fungoides 415

Granulomatous Slack Skin 415

Pagetoid Reticulosis (PR), Unilesional (Woringer–Kolopp) 417

Sézary Syndrome (SS) 418

Variant: Sézary Syndrome, Large Cell Transformation 420

CD30‐Positive Lymphoproliferative Disorders (LPD) of the Skin 423

Anaplastic Large Cell Lymphoma (ALCL) 424

Neutrophil‐Rich (Pyogenic) Anaplastic Large Cell Lymphoma 426

Lymphomatoid Papulosis 427

Differential Diagnosis: Hodgkin’s Lymphoma, Lymphocyte Predominance 429

Subcutaneous Panniculitis‐Like Lymphoma 431

Subcutaneous (Panniculitis-Like; Alpha/Beta) T‐Cell Lymphoma 431

Differential Diagnosis: Subcutaneous (Panniculitis‐Like) Gamma/Delta lymphoma 432

Differential Diagnosis: Lupus Panniculitis (Lupus Profundus) 433

Primary Cutaneous Peripheral Lymphoma (PTL), Unspecified (NOS) 434

Primary Cutaneous CD4‐positive (Acral) Small/Medium‐Sized T‐Cell Lymphoproliferative Disorder 435

Cutaneous Aggressive Epidermotropic CD8‐positive T‐Cell Lymphoma (Berti) 436

Differential Diagnosis: Febrile Ulceronecrotic PLEVA (Mucha–Habermann Disease) 437

Extranodal NK/T‐Cell Lymphoma, Nasal Type (Subcutaneous) 439

Hydroa Vacciniforme‐Like Lymphoma 440

Angioimmunoblastic T‐Cell Lymphoma 441

Cutaneous Mature B‐Cell Lymphoid Neoplasms (CBCL) 443

Cutaneous Marginal Zone B‐Cell Lymphoma (MZL; MALT Type) 444

Variant: Immunocytoma 447

Differential Diagnoses: Multiple Myeloma/Plasmacytoma 448

Primary Cutaneous Follicle Center Lymphoma (FCL) 449

Diffuse Large B‐Cell Lymphoma (DLBCL) 451

Variant: Cutaneous Diffuse Large B‐Cell Lymphoma (Leg Type) 451

Variant: T‐Cell‐Rich B‐Cell Lymphoma (DLBCL) 454

Cutaneous Spindle B‐Cell Lymphoma 455

Extracutaneous B‐Cell Lymphoma (BCL) with Frequent Skin Involvement 457

Mantle Cell Lymphoma 457

Burkitt’s Lymphoma (BL) 458

Lymphomatoid Granulomatosis (Liebow) (LYG) 460

Intravascular Lymphomas 461

Intravascular Large B‐Cell Lymphoma (IV‐LBCL) (Systemic Angioendotheliomatosis) 461

Intravascular T Cell Lymphoma 462

Secondary Skin Involvement in Leukemias/Lymphomas 463

Chronic Lymphocytic Leukemia (CLL) 463

Myeloid and Monocytic Leukemias 464

T‐Zone Lymphoma 466

Adult T‐Cell Leukemia/ Lymphoma (ATLL) 467

Immature Hematopoietic Malignancies 468

Blastic Plasmacytoid Dendritic Cell Neoplasm 468

Precursor Lymphoblastic Leukemia/Lymphoma 470

13 CUTANEOUS CYSTS 471

Cysts with Epithelial Lining 472

Stratified Squamous Epithelium 472

Epidermal (Infundibular) Cysts 472

Variant: Epidermal Proliferating Cyst 473

Variant: Epidermal Cyst with Pigment and Vellus Hairs 473

Vellus Hair Cyst 474

Trichilemmal (Isthmus‐Catagen) Cyst 475

Milia 476

Follicular Hybrid Cyst 477

Hidrocystoma (Cystadenoma) 478

Steatocystoma, Multiplex and Simplex 481

Dermoid Cyst 482

Pilonidal Sinus (Pilonidal Cyst) 484

Non‐Stratified Squamous Epithelium 485

Cutaneous Ciliated Cyst of the Lower Limb 485

Median Raphe Cyst 486

Cysts without Epithelial Lining (Pseudocysts) 487

Oral Mucous Cyst and Superficial Mucocele of the Lip 487

Digital Myxoid Cyst 488

Synovial Cyst (Ganglion) 490

Index 491