Pulmonary Leiomyoma in a Dromedary Camel ( Camelus Dromedarius )

During post-slaughter inspection of dromedary camel (Camelus dromedarius), two cases of leiomyoma were described in an eight and ten years old male camels. The neoplastic masses involved in the visceral pleura of one camel and lung tissue of another. Histopathologic features revealed proliferated neoplastic cells, resembling the smooth muscle cells, in the pleura and adjacent pulmonary tissue. The tumor masses appeared as circumscribed area of interlacing bundles of smooth muscle cells arranged in various directions and surrounded by connective tissue capsule. Moreover, the adjacent alveoli exhibited areas of atelectasis and emphysema. The origin of leiomyoma was not determined, but it was suggested that the neoplastic cells originated from smooth muscle layer of the pleural blood vessels.

The classification of lung neoplasm is slightly more difficult due to the possibilities of epithelium and mesenchymal metaplasia and occurrence of the intermediate or mixed forms.Leiomyoma is a benign tumor of smooth muscle cell primarily arising from the musculature tubular and hollow organs, such as the gastrointestinal, urinary, and genital tracts (Mobini and Kufuor-Mensah, 1987).Leiomyoma is a rare disease though to be derived from uterine leiomyoma.Despite leiomyoma is histological benign tumor, it has the possibility to metastasize to distant sites such as pelvic and retroperitoneal lymph nodes, omentum, inferior vena cava, right atrium, muscular tissue of the limb and the lung (Funakoshi et al., 2004).The current article documents the first case of pulmonary leiomyoma in camels.

Case History
During inspection of camel, which slaughtered at the Cairo Abattoir; Egypt.After slaughter, all tissues were examined macroscopically, and the lung tissues were brought to Benha University, Faculty of Veterinary Medicine and department of Pathology for histopathological examination.
The tissue samples for histopathology were fixed in 10% neutral buffered formalin, routinely processed, 5µm sectioned, and stained with Hematoxylin and Eosin (HE).Selected sections were stained by van Gieson's stain (Culling et al., 1985) .

Result
Two cases were detected microscopically as leiomyoma.The first case was observed in the visceral pleura and revealed thickening of the pleural tissue with proliferation of neoplastic cells, resembling the smooth muscle cells, in the pleura and adjacent pulmonary tissue (Fig. 1).While the second case was detected in the pulmonary tissue and appeared as circumscribed area of interlacing bundles of well-differentiated smooth muscle cells with minimal fibrous stroma, arranged in various directions and surrounded by connective tissue capsule (Fig. 2,3).The neoplastic cells were spindle cells with indistinguishable cytoplasmic borders and elongate, blunt-ended cigar shaped nuclei, no pleomorphism or mitotic activity was observed.The neoplastic mass gave positive reaction by Van-Gieson stain and appeared well differentiated from the surrounding connective tissue capsule (Fig. 4).Moreover, the adjacent alveoli revealed areas of atelectasis and emphysema.

Discussion
Benign pulmonary tumors are mostly single and generally asymptomatic.Among benign lung lesions leiomyomas are extremely rare (Burkhardt et al., 1981).It is assumed that Camelids are susceptible to all the various tumour types that affect domestic ungulates.Pulmonary leiomyoma described her is the primary.The microscopic examination of the camels' lungs showed presence of two cases of singular leiomyomatous lesions, one observed in the pleura and revealed thickening of the pleural tissue with proliferation of neoplastic cells resembling the smooth muscle cells.While the other case was detected in the pulmonary tissue and surrounded by connective tissue capsule; the adjacent alveoli revealed areas of atelectasis and emphysema.Our results are partially in agreement with (Lopez et al., 1997) who found anal leiomyoma in 2year-old heifer characterized by interlacing bundles of well-differentiated smooth muscle cells with abundant cytoplasm, irregular fusiform nuclei with vesiculated chromatin and scarce mitotic figures.
The tumors reported here was considered as benign tumor due to lack of the characteristic features associated with malignancy, including cellular pleomorphism, multinucleation, poor differentiation of fibers and hyperchromic nuclei with many mitotic figures and necrosis which may be evident grossly and microscopically (Swalec et al., 1989).Leiomyoma has been previously reported in a wide variety of animal species, include dogs, cats, humans, horses, cattle, sheep, and goats (Mobini and Kufuor-Mensah, 1987).In a previous study, two cases of leiomyoma were recorded in camel ' s uteri during an abattoir survey in Egypt (Moustafa et al., 2004); but have not been previously described in camels lung.In domestic animals, smooth muscle tumors arising within the respiratory tract are extremely rare, however, leiomyoma is still the most common type of gastrointestinal or genital tract stromal tumor (Meuten, 2002).Previous studies conducted with the pathological affections of camel's lung revealed rare neoplastic growth in the lung of these animals.(Taha et al., 2007) found one case of bronchoalveolar adenocarcinoma in lung tissues characterized by tall and differentiated cells with basely located nuclei, form sheets and glands, and secrete mucin.Nevertheless, leiomyoma was not previously recorded in the lung of camels according to available literature.Leiomyomas reported several times in the bovine reproductive tract (Saiyari et al., _______________ Gamal Wareth and Shawky Ahmed Moustafa (2013), International Journal of Veterinary Medicine: Research & Reports, DOI: 10.5171/2013.773813 1994), in esophagus and in rectum (Singh et al., 1988, Rajurkar et al., 1995, Lopez et al., 1997).Locally invasive intestinal leiomyomas and leiomyosarcomas were reported in Equine (Haven et al., 1991).In women and bitches, leiomyomas are among the most common reproductive tumors and are highly estrogen dependent in both species (Greenberg et al., 1993).Benign metastasizing leiomyoma is a very rare disease in which tissue from a benign uterine leiomyoma is detected as multiple nodules or as a solitary nodule in the lungs (Naito et al., 2011).Pathological comparison between the pulmonary leiomyoma and the original uterine tumor should provide confirmatory evidence but the immunohistochemical staining and the past history of uterine leiomyoma were not available.Although the origin of the tumor was not determined in this study; we suggested that, the neoplastic cells were originated from smooth muscle layer of the pleural blood vessels.

Fig
Fig. (1): Lung of Camel Showing Leiomyoma Appeared as Thickening of the Pleural Tissue with Proliferation of Neoplastic Cells; Resembling the Smooth Muscle Cells in Pulmonary Tissue (H&E Stain x200).