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Home , Acrospiroma, Aggressive angiomyxoma, Angiolipoleiomyoma, Clear cell acanthoma, Cylindroma, Epidermolytic acanthoma

CONTENTS

1. Epidermal Tumors ...... 1 Epithelial ...... 1 Epidermal and ...... 1 Human Papillomavirus-Associated Cyst (Verrucous Cyst) ...... 2 Proliferating Epidermal Cyst...... 2 Pigmented Follicular Cyst ...... 3 Cutaneous Keratocyst...... 3 Epithelial Cysts in Gardner’s Syndrome ...... 3 (Pilar Cyst, Isthmus-Catagen Cyst)...... 4 Proliferating Trichilemmal Cyst (Proliferating Trichilemmal Tumor, Pilar Tumor, Proliferating Pilar Tumor) ...... 5 Steatocystoma ...... 6 Dermoid Cyst...... 7 Eruptive Vellus Cyst...... 8 Cutaneous Cysts and Related Structures that May Be Ciliated...... 8 Other Cutaneous Cysts ...... 11 Benign Epidermal Tumors...... 14 Epidermal ...... 14 Acantholytic ...... 17 ...... 17 ...... 18 Seborrheic and its Variants...... 19 Large Cell Acanthoma...... 24 ...... 25 Clear Cell Papulosis...... 26 Pseudoepitheliomatous Hyperplasia...... 26 Premalignant and Malignant Epidermal Tumors...... 27 ...... 27 Porokeratosis ...... 31 Bowen’s Disease (Squamous Cell In Situ)...... 32 Erythroplasia of Queyrat...... 35 ...... 36 ...... 37 ...... 40 ...... 42 Adenosquamous Carcinoma ...... 44

ix Nonmelanocytic Tumors of the

Sarcomatoid Carcinoma (, Metaplastic Carcinoma)...... 45 Lymphoepithelioma-Like Carcinoma...... 46 Basal Cell Carcinoma...... 46 2. Neoplastic and Pseudoneoplastic Lesions of the Hair Follicles...... 71 Benign Follicular with Nongerminative Cellular Differentiation...... 71 Tumor of the Follicular Infundibulum ...... 71 Pilar Sheath Acanthoma...... 72 Winer’s Pore...... 72 ...... 73 ...... 73 Benign Proliferating Pilar Tumor...... 75 Benign Follicular Neoplasms with Germinative-Type Differentiation...... 76 ...... 77 ...... 78 Desmoplastic Trichoepithelioma...... 81 ...... 82 Trichogerminoma...... 85 Mixed Epithelial and Mesenchymal Follicular Proliferations...... 86 Basaloid Follicular ...... 86 ...... 87 Neoplasms Showing Differentiation Towards Follicle-Related Mesenchyme...... 89 ...... 89 Perifollicular ...... 89 ...... 90 Follicular ...... 91 Pilar ...... 91 Malignant Pilar Neoplasms ...... 92 ...... 92 Malignant Proliferating Pilar Tumor...... 95 Pilomatrix Carcinoma...... 97 Adnexal with Mixed Differentiation...... 98 Pilar ...... 98 Pseudoneoplastic Proliferations of Hair Follicles and Follicle-Related Mesenchyme. . 99 Hair Follicle Nevus...... 99 Linear Basal Cell Nevus...... 100 and Simplex ...... 101 Eruptive Vellus Hair Cyst...... 101 Neurofollicular and Pilar Neurocristic ...... 102 3. Tumors and Tumor-Like Conditions with Predominantly Sebaceous Differentiation. . . 117 Contents

Pseudoneoplastic Sebaceous Proliferations...... 117 ...... 117 Nevus Sebaceus...... 117 Benign Sebaceous Neoplasms...... 119 Sebaceous ...... 119 Superficial Epithelioma with Sebaceous Differentiation...... 122 ...... 123 Borderline Sebaceous Neoplasms...... 124 Basal Cell Carcinoma with Sebaceous Differentiation ...... 124 Malignant Sebaceous Neoplasms...... 126 ...... 126 4. Neoplasms and Pseudoneoplastic Proliferations of the Sweat , and Primary Neuroendocrine (Merkel Cell) Carcinoma...... 137 Benign Eccrine Sweat Neoplasms...... 137 Eccrine ...... 137 Eccrine ...... 138 ...... 139 Eccrine Poroma ...... 139 Eccrine Syringofibroadenoma ...... 141 Papillary Eccrine Adenoma (Tubulopapillary Eccrine )...... 143 Eccrine (Solid and Cystic Hidradenoma, Nodular Eccrine Hidradenoma...... 143 Benign Apocrine Neoplasms...... 146 Syringocystadenoma Papilliferum...... 147 Hidradenoma Papilliferum...... 148 Tubular Apocrine Adenoma...... 149 Sweat Gland Tumors with Mixed Differentiation...... 149 Benign Mixed Tumors of the Skin (Chondroid Syringoma)...... 149 Other Mixed Lineage Adnexal Tumors ...... 151 Malignant Sweat Gland Tumors...... 152 Eccrine Carcinomas...... 152 Eccrine Carcinomas that Are Histologically Definable as Primary Tumors...... 152 Eccrine Carcinomas that Histologically Simulate Metastatic Tumors...... 164 Apocrine Carcinomas...... 168 Apocrine Carcinomas that Are Histologically Definable as Primary Tumors...... 169 Apocrine Carcinomas that May Histologically Simulate Metastases...... 172 Adnexal Carcinomas of Uncertain or Mixed Lineage, with Sweat Glandular Elements...... 175 Lymphoepithelioma-Like Carcinoma...... 175

xi Nonmelanocytic Tumors of the Skin

Adnexal Carcinoma with Mixed Differentiation...... 177 Primary Neuroendocrine (Merkel Cell) Carcinoma...... 177 Pseudoneoplastic Lesions of Sweat Glands ...... 184 Eccrine and Apocrine Nevi...... 184 Syringometaplasia ...... 184 Eccrine and Apocrine ...... 185 5. Metastatic Neoplasms...... 201 Visceral Carcinomas that Involve the Skin...... 201 Clinical Features...... 201 Pathologic Findings...... 203 Specific Visceral Sources of Cutaneous ...... 204 Immunohistochemistry in the Determination of Primary Site...... 209 Primary Nonadnexal Epithelial Skin Tumors that May Resemble Metastatic Lesions. 209 Other Metastatic Neoplasms ...... 209 6. Fibrous Tissue Tumors ...... 215 Benign Fibrous Tissue Tumors...... 215 Fibroepithelial Polyps...... 215 Nevus...... 216 Fibrous Hamartoma of Infancy...... 217 ...... 218 Dermatomyofibroma...... 223 Angiofibroma and Related Lesions ...... 223 Plexiform Fibrohistiocytic Tumor ...... 226 Superficial Acral Fibromyxoma ...... 227 ...... 227 Sclerotic Fibroma...... 228 Collagenous Fibroma (Desmoplastic Fibroblastoma) ...... 229 Postoperative Spindle Cell ...... 230 Inflammatory Pseudotumor...... 230 ...... 231 Elastofibroma Dorsi...... 233 Giant Cell Tumor of Tendon Sheath...... 234 Peripheral Giant Cell Granuloma (Giant Cell )...... 235 Fibroma of Tendon Sheath...... 236 ...... 237 Recurrent Infantile Digital Fibroma...... 238 Myofibroma...... 238 Juvenile Hyaline Fibromatosis...... 240 ...... 241 Contents

Fibrous Tissue Tumors of Intermediate ...... 243 ...... 243 Dermatofibrosarcoma Protuberans ...... 244 Bednar’s Tumor (Pigmented Dermatofibrosarcoma Protuberans)...... 247 Giant Cell Fibroblastoma...... 248 Aggressive Angiomyxoma, Superficial Angiomyxoma, and Angiomyofibroblastoma ...... 249 Low-Grade Fibromyxoid ...... 252 ...... 253 Malignant Fibrous Tissue Tumors ...... 255 Malignant Fibrous ...... 255 Epithelioid Sarcoma...... 256 ...... 258 ...... 258 7. Vascular Tumors and Pseudotumors ...... 277 Vascular Nevus...... 277 Benign Vascular Neoplasms...... 277 Lymphangioma ...... 278 Cavernous and Capillary Hemangiomas...... 279 Lobular Capillary Hemangioma () and Related Lesions. . . . . 281 Kimura’s Disease...... 283 Epithelioid (Histiocytoid) Hemangioma...... 283 Acral Arteriovenous Tumor/(Arterio-)Venous Hemangioma...... 285 Hobnail/Targetoid/“Atypical” Hemangioma...... 287 Other Cutaneous Hemangioma Variants...... 289 Angiokeratoma...... 291 Borderline Vascular Tumors...... 292 Papillary Endovascular (Intralymphatic?) Angioendothelioma...... 292 Epithelioid Hemangioendothelioma...... 294 Spindle Cell Hemangioendothelioma (Hemangioma) ...... 296 Kaposiform Hemangioendothelioma ...... 297 Retiform Hemangioendothelioma...... 298 Other Hemangioendotheliomas ...... 299 Malignant Vascular Neoplasms ...... 299 Kaposi’s Sarcoma ...... 300 Angiosarcoma...... 304 Tumefactive Non-Neoplastic Vascular Proliferations...... 309 Lesions that Simulate Kaposi’s Sarcoma ...... 309 Potential Simulators of Angiosarcoma...... 313

xiii Nonmelanocytic Tumors of the Skin

Other Reactive Vascular Proliferations...... 314 8. Tumors and Tumor-Like Conditions Showing Neural, Nerve Sheath, and Adipocytic Differentiation...... 329 Neural Lesions ...... 329 Neuroma and Ganglioneuroma...... 329 ...... 330 Neurilemmoma ...... 333 Neurothekeoma...... 335 Benign Granular Cell Tumor...... 337 Peripheral Neuroepithelioma/Primitive Neuroectodermal Tumor...... 339 Nonepithelioid Malignant Peripheral Nerve Sheath Tumor...... 341 Epithelioid Malignant Peripheral Nerve Sheath Tumor ...... 344 Malignant Granular Cell Tumor ...... 345 Pseudotumors of the Skin Related to the Nervous System ...... 345 Rudimentary Meningocele (Primary Cutaneous Meningioma, Meningotheliomatous Hamartoma)...... 345 Cutaneous Glial Heterotopia (Nasal Glioma) ...... 347 Tumors with Adipocytic Differentiation...... 348 Variants...... 348 ...... 353 ...... 353 Adipocytic Pseudotumors...... 353 Nevus Lipomatosus ...... 353 Tumefactive Localized Lipedema...... 355 9. Tumors of Muscle, Cartilage, and Bone...... 365 Tumors...... 365 Smooth Muscle Hamartoma ...... 365 Leiomyoma...... 366 Cutaneous (Angiolipoleiomyoma)...... 369 Leiomyosarcoma ...... 370 Striated Muscle Tumors and Rhabdoid Tumor...... 372 Rhabdomyomatous Mesenchymal Hamartoma ...... 372 ...... 373 (Extrarenal) Malignant Rhabdoid Tumor...... 374 Cartilaginous Tumors and Parachordoma...... 375 Extraskeletal Chondroma...... 375 Subungual Osteochondroma and Exostosis ...... 376 Parachordoma ...... 376 Chondrosarcoma...... 377 Contents

Calcifying and Ossifying Tumors...... 377 Ossifying Fibromyxoid Tumor...... 377 Fibro-osseous Pseudotumor of the Digits ...... 378 Calcifying Aponeurotic Fibroma...... 379 Osteosarcoma...... 380 10. Histiocytic Proliferations ...... 389 Non-Langerhans Cell Histiocytic Infiltrates ...... 389 (Juvenile) Xanthogranuloma...... 389 Benign Cephalic Histiocytosis...... 392 Progressive Nodular Histiocytosis ...... 393 Generalized Eruptive Histiocytoma...... 394 Disseminatum...... 395 Reticulohistiocytosis ...... 396 Familial Histiocytic Dermatoarthritis ...... 399 Rosai-Dorfman Disease (Sinus Histiocytosis with Massive Lymphadenopathy). . . . 399 Malignant Histiocytosis...... 401 Langerhans Cell Histiocytosis and Indeterminate Cell Histiocytosis...... 402 Langerhans Cell Histiocytosis...... 402 Congenital Self-Healing Reticulohistiocytosis...... 404 Indeterminate Cell Histiocytosis...... 404 11. Plasmacellular Infiltrative Disorders ...... 415 Multiple Myeloma...... 415 Extraosseous Plasmacytoma...... 416 Macroglobulinemia of Waldenström...... 417 Castleman’s Disease...... 419 12. Cutaneous Mastocytosis...... 425 Systemic Mastocytosis ...... 425 Cutaneous Mastocytosis (Urticaria Pigmentosa)...... 426 13. Lymphoid Infiltrates, Lymphoma, and Hematopoietic Proliferations ...... 431 Lymphoid Infiltrates and Lymphomas ...... 431 Lymphocytoma Cutis (Reactive Lymphoid Infiltrate, Cutaneous Lymphoid Hyperplasia, Pseudolymphoma, Lymphadenosis Benigna Cutis)...... 432 B-Cell Neoplasms...... 435 Cutaneous Marginal Zone B-Cell Lymphoma (Mucosa-Associated Lymphoid Tissue [MALT] Lymphoma)...... 435 Follicular Lymphoma...... 438 Diffuse Large B-Cell Lymphoma ...... 440 Intravascular Large B-Cell Lymphoma...... 442 Lymphomatoid Granulomatosis...... 444

xv Nonmelanocytic Tumors of the Skin

Other B-Cell Lymphomas Involving the Skin...... 445 T-Cell and NK-Cell Neoplasms...... 447 Precursor T-Cell Lymphoblastic Lymphoma...... 447 Adult T-Cell Leukemia/Lymphoma...... 448 Extranodal NK/T-Cell Lymphoma, Nasal Type...... 451 Subcutaneous Panniculitis-Like T-Cell Lymphoma...... 453 ...... 456 Pagetoid Reticulosis...... 464 Granulomatous Slack Skin...... 465 Sézary’s Syndrome...... 466 Primary and Secondary Cutaneous Anaplastic Large Cell Lymphoma...... 469 Peripheral T-Cell Lymphoma, Not Further Specified (Including Lennert’s Lymphoma)...... 472 Angioimmunoblastic T-Cell Lymphoma...... 475 Lymphomatoid Papulosis ...... 477 Other T-Cell and NK-Cell Lymphomas Involving the Skin...... 480 Cutaneous Involvement in Hodgkin’s Disease ...... 480 Leukemia Cutis...... 483 Extramedullary Hematopoiesis ...... 486 Index ...... 513