Sarcomatoid Carcinoma in the Lung of an Egyptian Fruit Bat (Rousettus Aegyptiacus)

Abstract

Abstract. A sarcomatoid carcinoma was diagnosed in the lung of a 10-year-old captive Egyptian fruit bat (Rousettus aegyptiacus). Both carcinomatous and sarcomatous cytologic phenotypes were identified histologically. Cells of both types stained positive for pancytokeratin and S-100. Stromal cells stained positively for muscle actin. No staining for vimentin was noted in either neoplastic or normal internal control tissues. To the authors' knowledge, this is the first report of a pulmonary sarcomatoid carcinoma in a bat, and only the third report of sarcomatoid carcinoma outside the human literature.Key words: Egyptian fruit bats; immunohistochemistry; neoplasia; Rousettus aegyptiacus; sarcomatoid carcinoma.A 10-year-old, castrated, male Egyptian fruit bat (Rousettus aegyptiacus) was found to be weak and on the floor of its enclosure. The exhibit housed approximately 30 Egyptian fruit bats and 15 straw-colored fruit bats (Eidolon helvum). Clinical signs included hypothermia, severe dyspnea, and taut abdominal musculature. Diagnostic imaging revealed fluid in the abdomen, and 32 ml of serosanguineous fluid was removed via abdominocentesis; no subsequent analysis was done on this fluid. Supportive care was instituted, but the animal died several hours later.At necropsy, the carcass weighed 154 g and was markedly dehydrated. Muscle mass and fat stores were reduced. The penis was extruded, swollen and bruised at its tip. A solid 7 mm 3 3 mm cream-colored mass was adherent to the base of the heart and adjacent lung. A small amount of serosanguineous fluid was present in the abdominal cavity; there was no fluid in the pleural or pericardial spaces. All other tissues appeared normal. Differential diagnoses for the thoracic mass included a heart base tumor and pulmonary carcinoma. Tissue samples were fixed in 10% neutral buffered formalin, processed for histology by routine methods, and stained with hematoxylin and eosin.Histologically, the mass was composed of neoplastic cells and was contained largely within the lung. There were two distinct regions with differing cytologic phenotypes. The first was dominated by large, round epithelial cells that tended to form packets (carcinomatous component; Fig. 1). Nuclei were round to ovoid with scant chromatin and variably 0-2 nucleoli. There was 4-fold anisokaryosis and occasional multinucleate cells were evident. Mitotic figures were rare. The cytoplasm was abundant with a nucleus:cytoplasm ratio varying from approximately 1:1 to 1:10.The second region made up approximately 60% of the section examined and was comprised of spindle-shaped cells arranged in irregular swirls (sarcomatous component; Fig. 2). Nuclei of these cells were variably plump and oval to elongate, with finely stippled chromatin and occasionally a single nucleolus. Mitotic figures were rare. In a few

Beyond the Lab: What We Can Learn about Cancer from Wild and Domestic Animals

“…The majority of bat research focuses on their role as a pathogen reservoir [ 58 , 59 , 60 ]. Several studies have also highlighted their low incidence of tumors, and are reportedly limited to leiomyosarcoma and sacromatid carcinoma [ 61 , 62 , 63 ], which may have arisen due to positive selective pressure on gene expression linked to mechanisms associated with flight [ 64 , 65 , 66 ]. For example, the expression of DNA repair and antioxidant enzymes is elevated in bats, to counteract the formation of ROS as a by-product of increased energy demands of flight.…”

Chiroptera (Bats)

“…Histologically, the neoplastic cells were variably immunoreactive for both vimentin and cytokeratin, leading to a diagnosis of sarcomatoid carcinoma. 44 These are rare neoplasms in humans, and very few are diagnosed in veterinary species. 44…”

Mass extinctions, biodiversity and mitochondrial function: are bats ‘special’ as reservoirs for emerging viruses?

“…It is therefore interesting that unpublished anecdotal observations suggest that bats have a lower rate of tumorigenesis than most other animals. An extensive literature search revealed only a few recent papers describing tumors in Egyptian fruit bats [70][71][72].…”