Abstract. Ten cecal tumors were identified during the postmortem examination of seven horse carcasses at slaughter (one horse had three tumors). The multinodular and hemorrhagic tumors ranged from 1 to 10 cm in diameter and consisted of spindle cells arranged in thin, interconnected trabeculae that were often separated by sinuses filled with mucinous fluid, erythrocytes, and siderophages. Spindle cells of all tumors were immunopositive for vimentin, neuron-specific enolase, and c-kit protein but lacked reactivity with antibodies to glial fibrillary acidic protein, S100 protein, and desmin. In one tumor, spindle cells diffusely bound antibodies to synaptophysin. Most tumors contained focal reactivity to smooth muscle actin antibodies; one tumor reacted diffusely. Ultrastructurally, tumor cells were connected by desmosome-like structures and exhibited extended cell processes; some contained dense core neurosecretory granules. These equine stromal tumors appeared to share some characteristics with human gastrointestinal stromal tumors.

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SUMMARYThe objectives of the present study were to examine proventriculi of broiler chicks for lesions, and to classify and record the incidence of these lesions.Deep non-purulent necrotizing proventriculitis (accompanied by adenoepithelial hypertrophy and hyperplasia) was the most common (109/220 = 49.5%) light microscopic diagnosis in the proventriculi examined. Degenerating and necrotic alveolar secretory cells had amorphous, granular or vacuolated cytoplasm. Nuclei usually were either pyknotic, karyorrhectic or karyolytic; however, fewer attached or sloughed cells had swollen nuclei with marginated chromatin and clear centres. Basophilic inclusion bodies were never seen. In five cases examined ultrastructurally, hexagonal virus particles were found in intact nuclei (average size = 68.9 nm, n = 89), associated with unbound condensed chromatin, and within vacuolated spaces in the cytoplasm (average size = 62.3 nm, n = 109). DNA in situ hybridization failed to detect adenovirus or polyomavirus nucleic acids.The presence of intralesional virus suggests that a causal relationship might exist between the virus and the proventricular lesions.

Abstract. Spontaneous equine pulmonary granular cell tumors were diagnosed in six mature horses at slaughter. These tumors were grossly recognized as multiple (5/6) or single (1/6) creamy white, firm nodules. The tumors, located adjacent to bronchi and bronchioles, often invaded airways, resulting in partial to complete occlusion of the lumina. Neoplastic cells were rounded to polyhedral with numerous eosinophilic cytoplasmic granules that reacted uniformly positive with S-100 and neuron-specific enolase antibodies and multifocally with glial fibrillary acidic protein antibodies. These cells were negative for muscle-specific actin, lysozyme, cytokeratin, chromogranin A, and myelin basic protein antigens and did not stain with silver by the Grimelius technique. Uniformly blue-green and scattered pink intracytoplasmic granules were evident with luxol fast blue and periodic acid-Schiff counterstain for myelin and myelin breakdown products. Histochemical and immunohistochemical staining results of these tumors suggest that they are composed primarily of myelinating Schwann cells with lesser numbers of scattered nonmyelinating Schwann cells. The morphologic features of the equine pulmonary granular cell tumors are strikingly similar to those of endobronchial granular cell tumors of human beings.