Idiopathic multifocal myocardial atrophy with fibrosis and fatty infiltration involving Purkinje fibres in a 13-year-old Arabian broodmare: Histopathological features.

Myocardial atrophy with fibrosis and fatty infiltration involving the cardiac conduction system is relatively unusual in horses. We herein report of such a case in a 13-year-old Arabian broodmare that had spontaneously died on a paddock. An autopsy revealed multifocal myocardial atrophy with concomitant fibrosis and fatty infiltration in both the ventricles and interventricular septum. The Purkinje fibres in the ventricles and interventricular septum were surrounded by thick fibrous or adipose tissues adjacent to atrophic myocardial cells. Myocardial fibrosis and fatty infiltration were likely secondary to myocardial atrophy, occurring as a pathological response triggered by the repair of muscular wall injury. However, there were no major vascular pathologies (e.g. atherosclerosis and arteriosclerosis); hence, the pathogenesis of myocardial atrophy was unclear. There was no evidence of myocardial atrophy ̵ induced pathologies such as infarct, ischaemic lesions, myocardial degeneration, myocarditis and endocarditis. However, such an unusual histopathological pattern may be associated with rapid clinical deterioration and death.

Hypoglycemia associated with disseminated metastatic tonsillar squamous cell carcinoma producing insulin-like growth factor-I in a Pomeranian dog.

A 13-year-old spayed female Pomeranian dog was presented for persistent, severe hypoglycemia (37 mg/dL; reference interval [RI] 75-128 mg/dL). Progressive nonregenerative anemia (hematocrit 23.3%-15.9%; RI 37.0%-55.0%) and severe thrombocytopenia (36 000/µL; RI 200-500 000/µL) were also noted. The serum insulin concentration was low (0.24 ng/mL; RI 0.302-1.277 ng/mL). Computed tomography revealed multiple splenic nodules (1-6 mm in diameter) and several hepatic nodules (7.6, 12 mm in diameter). Ultrasound-guided fine-needle aspiration of the splenic and hepatic nodules revealed low numbers of epithelial cells with mild cellular atypia, suggestive of a metastatic epithelial tumor, but the primary site was unknown at that time. On careful oral examination under general anesthesia, an enlarged right tonsil was noted grossly, and histopathologic examination of the tonsil diagnosed squamous cell carcinoma. Bone marrow aspirates and biopsies of the splenic and hepatic nodules were performed; all samples were diagnosed as metastatic carcinoma on histopathologic examination. No nodules were present in the pancreas, despite careful palpation during exploratory laparotomy. On immunohistochemistry, the neoplastic cells were positive for cytokeratin AE1/3 and insulin-like growth factor (IGF)-I but were negative for chromogranin A, PGP9.5, insulin, and inconclusive for IGF-II. This is the first report of a primary IGF-I-producing squamous cell carcinoma in the tonsil of a dog with metastases to bone marrow, liver, and spleen, resulting in hypoglycemia.