CONTENTS 1. Epidermal Tumors . 1 Epithelial Cysts. 1 Epidermal Cyst and Milium. 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 Trichilemmal Cyst (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 Hair Cyst. 8 Cutaneous Cysts and Related Structures that May Be Ciliated. 8 Other Cutaneous Cysts . 11 Benign Epidermal Tumors. 14 Epidermal Nevus . 14 Acantholytic Acanthoma. 17 Epidermolytic Acanthoma. 17 Warty Dyskeratoma. 18 Seborrheic Keratosis and its Variants. 19 Large Cell Acanthoma. 24 Clear Cell Acanthoma. 25 Clear Cell Papulosis. 26 Pseudoepitheliomatous Hyperplasia. 26 Premalignant and Malignant Epidermal Tumors. 27 Actinic Keratosis. 27 Porokeratosis . 31 Bowen’s Disease (Squamous Cell Carcinoma In Situ). 32 Erythroplasia of Queyrat. 35 Bowenoid Papulosis. 36 Squamous Cell Carcinoma. 37 Verrucous Carcinoma. 40 Keratoacanthoma. 42 Adenosquamous Carcinoma . 44 ix Nonmelanocytic Tumors of the Skin Sarcomatoid Carcinoma (Carcinosarcoma, Metaplastic Carcinoma). 45 Lymphoepithelioma-Like Carcinoma. 46 Basal Cell Carcinoma. 46 2. Neoplastic and Pseudoneoplastic Lesions of the Hair Follicles. 71 Benign Follicular Neoplasms with Nongerminative Cellular Differentiation. 71 Tumor of the Follicular Infundibulum . 71 Pilar Sheath Acanthoma. 72 Winer’s Pore. 72 Trichoadenoma . 73 Trichilemmoma. 73 Benign Proliferating Pilar Tumor. 75 Benign Follicular Neoplasms with Germinative-Type Differentiation. 76 Trichofolliculoma. 77 Trichoepithelioma. 78 Desmoplastic Trichoepithelioma. 81 Pilomatricoma. 82 Trichogerminoma. 85 Mixed Epithelial and Mesenchymal Follicular Proliferations. 86 Basaloid Follicular Hamartoma. 86 Trichoblastoma. 87 Neoplasms Showing Differentiation Towards Follicle-Related Mesenchyme. 89 Trichodiscoma . 89 Perifollicular Fibroma. 89 Fibrofolliculoma. 90 Follicular Myxoma. 91 Pilar Leiomyoma . 91 Malignant Pilar Neoplasms . 92 Trichilemmal Carcinoma. 92 Malignant Proliferating Pilar Tumor. 95 Pilomatrix Carcinoma. 97 Adnexal Carcinomas with Mixed Differentiation. 98 Pilar Leiomyosarcoma . 98 Pseudoneoplastic Proliferations of Hair Follicles and Follicle-Related Mesenchyme. 99 Hair Follicle Nevus. 99 Linear Basal Cell Nevus. 100 Steatocystoma Multiplex and Simplex . 101 Eruptive Vellus Hair Cyst. 101 Neurofollicular and Pilar Neurocristic Hamartomas. 102 3. Tumors and Tumor-Like Conditions with Predominantly Sebaceous Differentiation. 117 Contents Pseudoneoplastic Sebaceous Proliferations. 117 Sebaceous Hyperplasia. 117 Nevus Sebaceus. 117 Benign Sebaceous Neoplasms. 119 Sebaceous Adenoma. 119 Superficial Epithelioma with Sebaceous Differentiation. 122 Sebaceoma. 123 Borderline Sebaceous Neoplasms. 124 Basal Cell Carcinoma with Sebaceous Differentiation . 124 Malignant Sebaceous Neoplasms. 126 Sebaceous Carcinoma. 126 4. Neoplasms and Pseudoneoplastic Proliferations of the Sweat Glands, and Primary Neuroendocrine (Merkel Cell) Carcinoma. 137 Benign Eccrine Sweat Gland Neoplasms. 137 Eccrine Cylindroma. 137 Eccrine Spiradenoma. 138 Syringoma . 139 Eccrine Poroma . 139 Eccrine Syringofibroadenoma . 141 Papillary Eccrine Adenoma (Tubulopapillary Eccrine Hidradenoma). 143 Eccrine Acrospiroma (Solid and Cystic Hidradenoma, Nodular Eccrine Hidradenoma. 143 Benign Apocrine Sweat Gland 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 Hidrocystomas. 185 5. Metastatic Neoplasms. 201 Visceral Carcinomas that Involve the Skin. 201 Clinical Features. 201 Pathologic Findings. 203 Specific Visceral Sources of Cutaneous Metastasis. 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 Connective Tissue Nevus. 216 Fibrous Hamartoma of Infancy. 217 Dermatofibroma. 218 Dermatomyofibroma. 223 Angiofibroma and Related Lesions . 223 Plexiform Fibrohistiocytic Tumor . 226 Superficial Acral Fibromyxoma . 227 Pleomorphic Fibroma. 227 Sclerotic Fibroma. 228 Collagenous Fibroma (Desmoplastic Fibroblastoma) . 229 Postoperative Spindle Cell Nodule. 230 Inflammatory Pseudotumor. 230 Keloid. 231 Elastofibroma Dorsi. 233 Giant Cell Tumor of Tendon Sheath. ..