Preface, xiii Part I Overview of the Diagnostic Process, 1 1 Overview of Diagnosis, Categorization, Grading, and Staging, 3 Identification of the process, 3 Identification of tumor types, 6 Grading, 6 Staging, 9 Staging versus clinical behavior, 10 Tumor classification by cell type: epithelial, mesenchymal, round cell melanoma, 13 Epithelial tumors, 13 Mesenchymal tumors, 29 Round cell tumors, 37 Mast cell tumor, 37 Lymphoma, 43 Histiocytoma, 46 Plasmacytoma, 48 Melanoma, 48 Conclusion, 51 References, 52 Part II Case Studies, 57 2 Selected Lesions of the Head and Neck, 59 Bone tumors of the head, 59 Osteoma, 59 Osteosarcoma, 59 Mass lesions of the ear canal, 62 Aural polyp, 62 Ceruminous adenoma, 63 Ceruminous carcinoma, 64 Mass lesions of the external ear pinna, 65 Histiocytoma, 65 Squamous cell carcinoma, 66 Mass lesions of the conjunctiva and nictitans, 67 Papilloma, 67 Squamous cell carcinoma, 68 Hemangiosarcoma, 70 Melanoma, 71 Eyelid masses, 72 Meibomian gland adenoma, 72 Spindle cell tumor, 72 Lesions of the oral and nasal mucosal epithelium, 74 Eosinophilic inflammation, 74 Lymphoplasmacellular inflammation, 76 Lymphoma, 77 Epulis, 78 Acanthomatous epulis, 78 Ossifying epulis, 79 Viral papilloma, 80 Squamous cell carcinoma, 81 Melanoma, 82 Nasal cavity tumors, 83 Adenocarcinoma, 84 Chondrosarcoma, 85 Mass lesions of the canine and feline muzzle skin, 86 Sebaceous gland nodular hyperplasia, 86 Sebaceous gland adenoma, 87 Sebaceous epithelioma, 87 Trichoblastoma (Basal cell tumor), 88 Mast cell tumor, 89 Plasma cell tumor, 91 Mass lesions of the submandibular region, 92 Reactive lymph node, 93 Malignant lymphoma, 94 Normal salivary gland, 95 Salivary mucocele, 95 Salivary gland carcinoma, 96 Ventral neck masses, 97 Thyroid adenoma, 98 Thyroid carcinoma, 99 Parathyroid adenoma, 100 Additional reading, 101 Bone tumors of the head, 101 Mass lesions of the ear canal, 101 Ceruminous gland carcinoma, 101 Mass lesions of the external ear pinna, 101 Histiocytoma, 101 Squamous cell carcinoma, 101 Mass lesions of the conjunctiva and nictitans, 101 Eyelid masses, 102 Meibomian gland adenoma, 102 Spindle cell tumor, 102 Lesions of the oral and nasal mucosal epithelium, 102 Eosinophilic inflammation, 102 Lymphoplasmacellular inflammation, 102 Acanthomatous epulis, 102 Viral papilloma, 102 Squamous cell carcinoma, 102 Melanoma, 102 Nasal cavity tumors, 102 Adenocarcinoma, 103 Chondrosarcoma, 103 Mass lesions of the canine and feline muzzle skin, 103 Sebaceous gland nodular hyperplasia, 103 Sebaceous gland adenoma, 103 Sebaceous epithelioma, 103 Trichoblastoma (Basal cell tumor), 103 Mast cell tumor, 103 Plasma cell tumor, 103 Mass lesions of the submandibular region, 103 Reactive lymph node, 103 Malignant lymphoma, 103 Normal salivary gland, 104 Salivary mucocele, 104 Salivary gland carcinoma, 104 Ventral neck masses, 104 Thyroid carcinoma, 104 3 Selected Lesions of the Limbs, Paws, and Digits, 105 Bone lesions, 105 Periosteal hyperplasia, 105 Osteosarcoma, 105 Subungual tumors, 108 Melanoma, 108 Squamous cell carcinoma, 110 Digital skin and nail bed lesions, 111 Calcinosis circumscripta, 111 Plasmacellular pododermatitis, 112 Papilloma, 112 Fibroadnexal hyperplasia, 114 Stromal tumors of the limb, 116 Canine low-grade spindle cell tumor, 116 Feline spindle cell tumor, 118 Lipoma, 119 Liposarcoma, 121 Synovial sarcoma, 122 Additional reading, 123 Bone lesions, 123 Subungual tumors, 123 Melanoma, 123 Squamous cell carcinoma, 124 Digital skin and nail bed lesions, 124 Calcinosis circumscripta, 124 Plasmacellular pododermatitis, 124 Papilloma, 124 Fibroadnexal hyperplasia, 124 Stromal tumors of the limb, 124 4 Selected Genital and Perineal Masses, 127 Perineal masses, 127 Rectal polyp, 127 Perianal gland adenoma, 127 Perianal gland carcinoma, 129 Anal sac apocrine gland carcinoma, 130 Masses of the external genitalia, 132 Transmissible venereal tumor, 132 Mast cell tumor, 133 Additional reading, 134 Perineal masses Rectal polyp, 134 Perianal gland adenoma, 134 Perianal gland carcinoma, 134 Anal sac apocrine gland carcinoma, 135 Masses of the external genitalia, 135 Transmissible venereal tumor, 135 Mast cell tumor, 135 5 Selected Lesions of the Skin and Subcutis of the Trunk, 137 Mass lesions of the dorsal trunk, 137 Calcinosis cutis, 137 Follicular cyst, 137 Cystic adnexal tumors-trichoepithelioma, keratoacanthoma, 138 Apocrine adenoma, 141 Apocrine and sebaceous carcinoma, 141 Sebaceous carcinoma, 143 Lipoma, 143 Canine well-differentiated spindle cell proliferation, 144 Canine spindle cell tumor, middle grade, 146 Canine spindle cell tumor, high grade, 146 Feline spindle cell tumor, 149 Canine cutaneous lymphoma, 151 Mast cell tumor, 153 Canine histiocytoma, 154 Histiocytosis, 155 Dorsal tail head masses, 157 Pilomatricoma, 157 Melanoma, 158 Sebaceous adenoma, 160 Perianal gland adenoma, 161 Ventral trunk vascular lesions of the skin and subcutis, 161 Hemangioma, 162 Hemangiosarcoma, 162 Mass lesions of the mammary gland, 164 Fibroepithelial hyperplasia, 164 Mammary gland adenoma, 165 Complex adenoma, 165 Mixed mammary tumor, 167 Mammary carcinoma, 167 Additional reading, 171 Mass lesions of the dorsal trunk, 171 Calcinosis cutis, 171 Follicular cyst, 171 Cystic adnexal tumors-tricoepithelioma, keratoachanthoma, 171 Apocrine adenoma, 171 Apocrine and sebaceous carcinoma, 171 Lipoma, 171 Canine well-differentiated spindle cell proliferation, 171 Canine spindle cell tumor, mid grade, 171 Canine spindle cell tumor, high grade, 171 Feline spindle cell tumor, 171 Canine cutaneous lymphoma, 172 Mast cell tumor, 172 Canine histiocytoma, 172 Histiocytosis, 172 Dorsal tail head masses, 172 Pilomatricoma, 172 Melanoma, 172 Sebaceous adenoma, 172 Perianal gland adenoma, 172 Ventral trunk vascular lesions of the skin and subcutis, 173 Hemangioma, 173 Hemangiosarcoma, 173 Mass lesions of the mammary gland, 173 Fibroepithelial hyperplasia, 173 Mammary carcinoma, 173 6 Selected Lesions of the Thoracic Viscera, 175 Cardiac tumors, 175 Hemangiosarcoma, 175 Malignant plasma cell tumor, 175 Pulmonary mass lesions, 178 Pulmonary carcinoma, 178 Pulmonary hemangiosarcoma, 180 Pulmonary adenomatosis, 181 Mediastinal tumors, 184 Mediastinal malignant lymphoma, 184 Thymoma, 186 Additional reading, 187 Cardiac tumors, 187 Hemangiosarcoma, 187 Pulmonary mass lesions, 187 Pulmonary carcinoma, 188 Mediastinal tumors, 188 Mediastinal malignant lymphoma, 188 Thymoma, 188 7 Selected Lesions of the Abdominal Viscera, 189 Diseases that result in liver enlargement, 189 Vacuolar hepatopathy, 189 Bile duct hyperplasia, 189 Hepatocellular neoplasia, 191 Bile duct carcinoma, 193 Hepatic hemangiosarcoma, 194 Gastrointestinal lesions, 194 Eosinophilic inflammatory bowel disease, 195 Lymphoplasmacellular inflammatory bowel disease, 196 Gastrointestinal malignant lymphoma, 197 Gastrointestinal adenocarcinoma, 198 Gastrointestinal spindle cell tumor, 199 Kidney and bladder masses, 200 Pyogranulomatous inflammatory disease suggestive of FIP, 200 Renal carcinoma, 201 Renal malignant lymphoma, 202 Urinary bladder cystitis with reactive epithelial hyperplasia, 203 Urinary bladder polyp, 204 Transitional cell carcinoma, 205 Splenomegaly and splenic masses, 206 Extramedullary hematopoiesis, 207 Lymphoid nodular hyperplasia, 207 Malignant lymphoma, 209 Mast cell tumor, 209 Splenic torsion, 211 Splenic hematoma, 211 Splenic hemangiosarcoma, 214 Splenic histiocytic sarcoma, 216 Splenic malignant fibrous histiocytoma, 217 Additional reading, 218 Diseases that result in liver enlargement, 218 Vacuolar hepatopathy, 218 Nodular regeneration with bile duct hyperplasia, 218 Hepatocellular neoplasia, 218 Bile duct carcinoma, 218 Hepatic hemangiosarcoma, 218 Lymphoma, 218 Gastrointestinal lesions, 218 Eosinophilic inflammatory bowel disease, 219 Lymphoplasmacellular inflammatory bowel disease, 219 Gastrointestinal malignant lymphoma, 219 Gastrointestinal adenocarcinoma, 219 Gastrointestinal spindle cell tumor, 219 Kidney and bladder masses, 219 Pyogranulomatous inflammato.