List of Contributors xiii Preface xiv Acknowledgments xv 1 Pathology of the Eye and Periocular Tissues 1 Joseph S. Haynes Introduction 1 Prefixation Preparation 1 Fixation of Eyes for Histopathology 1 Sectioning 2 Processing and Staining 2 Ocular Structure and Development 2 Cornea 3 General Corneal Reactions to Injury 4 Developmental and Degenerative Corneal Disease 5 Corneal Dermoid 5 Corneal Erosions and Ulcers 5 Corneal Sequestration 7 Corneal Endothelial Dystrophy and Mineralization 8 Corneal Stromal Dystrophy and Mineralization 8 Inflammatory Disease of the Cornea 8 Keratitis 8 Keratitis sicca 9 Canine Pannus Keratitis (Chronic Superficial Keratitis) 10 Feline Herpetic Keratitis 10 Feline Eosinophilic Keratitis 10 Mycotic Keratitis 11 Equine Corneal Stromal Abscess 11 Uvea 11 General Uveal Reactions to Injury 12 Developmental and Degenerative Uveal Disease 13 Goniodysgenesis and Pectinate Ligament Dysplasia 14 Persistent Pupillary Membrane 14 Choroidal Hypoplasia 14 Hypertensive Vasculopathy 15 Inflammatory Disease of the Uvea and Ocular 15 Uveitis 15 Lymphoplasmacytic Anterior Uveitis 16 Phacoclastic Uveitis/Endophthalmitis 19 Phacolytic Uveitis 19 Equine Recurrent Uveitis 19 Uveitis Due to FIP Coronavirus 19 Canine Uveodermatologic Syndrome (VKH-­like Syndrome) 19 Pigmentary Uveitis 20 Endophthalmitis and Panophthalmitis 20 Bacterial Endophthalmitis 22 Ocular Blastomycosis 22 Ocular Cryptococcosis 22 Ocular Coccidioidomycosis 22 Ocular Histoplasmosis 24 Ocular Protothecosis 24 Lens 25 General Lens Reactions to Injury 25 Lens Luxation 25 Developmental and Degenerative Disease of the Lens 25 Microphakia and Aphakia 25 Persistent Pupillary Membrane, Persistent Primary (Hyperplastic) Vitreous, Persistent Posterior Tunica Vasculosa Lentis, and Persistent Hyaloid Artery 26 Cataract 27 Inflammatory Disease of the Lens 28 Phacitis 28 Retina 29 General Retinal Reactions to Injury 30 Developmental and Degenerative Retinal Disease 30 Retinal Dysplasia 30 Lysosomal Storage Diseases 30 Cystic Retinal Degeneration 31 Inherited Retinal Dysplasia and/or Degeneration (Progressive Retinal Atrophy) 31 Nutritionally Induced Retinopathy 32 Toxic Retinopathy 32 Ischemic and Infarctive Retinopathy 33 Glaucoma 33 Sudden Acquired Retinal Degeneration Syndrome 34 Retinal Detachment 35 Inflammatory Disease of the Retina 36 Retinitis 36 Optic Nerve 36 Developmental and Degenerative Disease of the Optic Nerve 36 Hypoplasia of the Optic Nerve and/or Optic Chiasm 36 Axonal Degeneration and Atrophy of the Optic Nerve 36 Cavitation of Optic Disk 36 Canine Ocular Gliovascular Syndrome 37 Inflammatory Disease of the Optic Nerve 37 Optic Neuritis 37 Granulomatous Meningoencephalitis 38 Sclera 38 Developmental and Degenerative Scleral Disease 39 Scleral Ectasia 39 Inflammatory Disease of the Sclera 39 Lymphoplasmacytic Scleritis 39 Nodular Granulomatous Episcleritis and Necrotizing Scleritis 40 Eyelids, Conjunctiva and Retrobulbar Tissues 40 Developmental Disease of the Eyelids 40 Inflammatory Disease of the Eyelids 40 Granulomatous Blepharitis/Meibomian Adenitis 40 Marginal Nodular Blepharitis/Meibomian Adenitis 42 Inflammatory Disease of the Conjunctiva, Membrana Nictitans, and Retrobulbar Tissues 42 Conjunctivitis 42 Nodular Granulomatous Episcleritis/Conjunctivitis 42 Periocular/Retrobulbar Cellulitis/Abscess 42 Neoplasia of the Eye and Periocular Tissues 43 Neoplasia of the Cornea 43 Neoplasia of the Uvea 45 Intraocular Melanoma and Uveal Melanocytosis 45 Iridociliary Tumors 45 Anterior Uveal Sarcoma of Blue-­Eyed Dogs 46 Intraocular Osteosarcoma 46 Intraocular Adenocarcinosarcoma (Malignant Mixed Tumor) 48 Lymphoma 48 Neoplasia of the Lens 50 Trauma-­Induced Intraocular Sarcoma of Cats 50 Neoplasia of the Retina 50 Neoplasia of the Eyelids 50 Palpebral Melanocytoma and Malignant Melanoma 50 Squamous Cell Carcinoma 50 Squamous Papilloma 50 Meibomian Gland Tumors 52 Neoplasia of the Conjunctiva and Membrana Nictitans 52 Squamous Cell Carcinoma 52 Adenocarcinoma of Gland of Third Eyelid (Membrana Nictitans) 54 Epibulbar Melanoma 54 Neoplasia of Retrobulbar Tissues 54 Retrobulbar Meningioma 54 Retrobulbar Peripheral Nerve Sheath Tumor 55 Lymphoma 55 Adenoma/Adenocarcinoma of Lacrimal Gland or Zygomatic Salivary Gland 55 Canine Orbital Lobular Adenoma 57 References and Additional Readings 57 2 Pathology of the Bones and Joints 59 Joseph S. Haynes Introduction 59 Specimen Preparation, Fixation, and Demineralization 59 Bone Structure and Physiology 60 Development of Bone and Cartilage 61 Basic Reactions of Bone to Injury 62 Hypoplastic/Dysplastic Bone Growth 62 Loss of Bone 63 Excessive Production of Bone 63 Osteonecrosis 64 Inflammation of Bone 65 Neoplasia of Bone 68 Joint Structure and Physiology 68 Basic Reactions of Joints to Injury 68 Degenerative Changes in Articular Cartilage 69 Inflammation of Articular Cartilage and Chondronecrosis 70 Inflammation of the Synovial Membrane and Joint Capsule 71 Diseases of Bone 72 Developmental Disorders and Anomalies 72 Osteochondrosis 72 Physeal Dysplasia in Cats 73 Chondrodysplasia 73 Osteochondromatosis (Multiple Cartilaginous Exostoses) 73 Hyperostotic Diseases of Bone 74 Hypertrophic (Pulmonary) Osteopathy 74 Canine Hepatozoonosis 74 Hyperostoses of Nutritional Origin 74 Hyperostoses of Unknown Cause 74 Inflammatory Diseases of Bone 75 Osteomyelitis Caused by Bacterial Infection 75 Osteomyelitis Caused by Fungal Infection 76 Canine Metaphyseal Osteopathy (Canine Hypertrophic Osteodystrophy) 76 Osteonecrosis and Bone Infarction 77 Necrosis of the Femoral Head and Legg-Calve-Perthes Disease 77 Bone Infarction 77 Neoplasia of Bone 78 Osteoma 78 Osteosarcoma 78 Chondroma 80 Chondrosarcoma 82 Multilobular Tumor of Bone 82 Osteochondroma 83 Giant Cell Tumor 83 Multiple Myeloma 83 Chordoma 84 Hemangiosarcoma 84 Ossifying Fibroma 84 Diseases of Joints 85 Osteochondrosis Dissecans 85 Infectious Arthritis due to Bacteria 86 Lyme Disease 86 Autoimmune and Immune-­Mediated Arthritis 86 Chronic Osteoarthritis 86 Neoplasms of Joints 87 References and Additional Readings 89 3 Pathology of the Skin 90 Joseph S. Haynes Introduction 90 Specimen Preparation and Fixation 90 Basic Reactions of Skin to Injury 90 Inflammation of the Skin: Dermatitis 90 Microscopic Patterns of Cutaneous Inflammation 91 Acute Dermatitis 91 Chronic Dermatitis 94 Abnormal Keratinization 95 Alopecia 96 Abnormal Pigmentation 96 ­Diseases of the Skin 96 Developmental Disorders and Anomalies of the Skin 96 Ichthyosis 96 Primary Seborrhea 96 Hyperplastic Dermatosis of the West Highland White Terriers 97 Zinc Responsive Dermatosis 97 Black-­Hair Follicular Dysplasia and Color Mutant Alopecia 98 Collagen Dysplasia 98 Degenerative, Atrophic, and Necrotizing Diseases of the Skin 99 Endocrine-­Related Disease 99 Superficial Necrolytic Dermatitis 100 Toxic Epidermal Necrolysis 101 Cutaneous Infarction 101 Inflammatory Diseases of the Skin 101 Allergic Skin Diseases 101 Feline Miliary Dermatitis 103 Autoimmune Skin Diseases 107 Bacterial Skin Disease 111 Pyoderma 112 Nocardiosis and Actinomycosis 112 Fungal Skin Disease 112 Dermatophytosis 112 Additional Fungal Skin Disease 112 Parasitic Skin Disease 113 Demodectic Mange 113 Sarcoptic and Notoedric Mange (Scabies) 115 Cutaneous Habronemiasis 116 Miscellaneous Inflammatory Skin Diseases 116 Acral Lick Dermatitis 116 Chronic Otitis Externa 117 Pyogranulomatous Panniculitis 117 Sebaceous Adenitis 117 Neoplasms and Cystic Lesions of the Skin 117 Epithelial Neoplasms 117 Squamous Papilloma 117 Inverted Viral Squamous Papilloma 119 Cutaneous Horn 119 Canine and Feline Viral Plaque 119 Actinic Keratosis 119 Squamous Cell Carcinoma 120 Squamous Cell Carcinoma 121 Basosquamous Carcinoma 124 Infundibular Keratinizing Acanthoma (Intracutaneous Cornifying Epithelioma) 124 Subungual Keratoacanthoma 125 Trichoblastoma (Basal Cell Tumor) 125 Trichoblastoma 125 Trichoepithelioma 125 Pilomatricoma 129 Apocrine Gland Tumors 131 Anal Sac Apocrine Adenocarcinoma 132 Ceruminous Gland Tumors 133 Sebaceous Gland Tumors 133 Hepatoid/Perianal Gland Tumors 135 Eccrine Gland Tumors 135 Melanotic Tumors 137 Mesenchymal Neoplasms 138 Canine Soft Tissue Sarcomas 138