Cloacal fibrosarcoma in a canary (Serinus canaria).
Abstract: A 1-year old, male canary (Serinus canaria) with a history of an enlarged abdomen of several days duration died acutely and was submitted for necropsy. Results revealed a yellow to tan hard mass, 2 cm in diameter, adherent to the cloacal wall. Histologically, the mass was composed of interlacing bundles of pleomorphic spindle cells with numerous and bizarre mitotic figures. Neoplastic cells were positive for vimentin and negative for desmin and actin and showed ultrastructural features (dilated stacks of rough endoplasmic reticulum, intermediate filaments, rare collagen secretion granules, lack of external lamina) typical of fibroblasts. Based on these results, the diagnosis was cloacal fibrosarcoma, previously not reported in canaries.
Key words: fibrosarcoma, cloaca, avian, canary, Serinus canaria
A 1-year-old, male canary (Serinus canaria) was presented to the veterinary clinic for evaluation of a mass within the abdominal cavity. On physical examination, the bird was thin and had a pronounced abdominal swelling. No other physical abnormalities were observed, and results of both a complete blood cell count and plasma biochemical analysis were within reference intervals. The bird died suddenly a few days after presentation, and a complete postmortem examination of the canary was performed. Gross examination revealed a large, 2-cm-diameter, yellow to tan, hard mass, both externally and on the cut surface, adherent to the cloacal wall, but with an intact mucosa (Fig 1). The intestinal tract proximal to the mass was severely dilated and contained abundant fecal material. Sections of the mass were fixed in 10% neutral-buffered formalin, routinely processed, and stained with hematoxylin and eosin and Masson trichrome stains. Immunohistochemistry for vimentin (mouse monoclonal antibody, clone 3B4, Dako Corp, Carpinteria, CA, USA), smooth muscle actin (mouse monoclonal, clone 1A4, Dako), cytokeratin (mouse monoclonal, clones AEI/AE3, Dako), desmin (mouse monoclonal, clone D33, Dako), and von Willebrand factor (rabbit polyclonal, Dako) were also performed on sections of the mass with a streptavidin-biotin peroxidase complex method. Formalin-fixed canine, chicken, and canary skins were used as positive controls. For transmission electron microscopy, randomly chosen, formalin-fixed sections of the mass were fixed in 2.5% glutaraldehyde (pH 7.2) and postfixed in 1% osmium tetroxide in 0.1 M cacodylate buffer. The samples were subsequently dehydrated through an ethanol series, rinsed in propylene oxide, and embedded in epoxy resin (Durcupan ACM Fluka, Sigma-Aldrich, St Louis, MO, USA). Electron micrographs were taken on ultrathin sections (70 nm) with a Zeiss EM9000 electron microscope (Carl Zeiss, Oberkochen, West Germany). Unless otherwise stated, all chemicals for transmission electron microscopy were purchased from Electron Microscopy Sciences (Fort Washington, PA, USA).
On histologic examination, a partially encapsulated and densely cellular mass infiltrated the external muscular layer of the proctodeum (Fig 2). The mass was composed of haphazardly arranged bundles of pleomorphic, spindle-shaped, occasionally polygonal cells (Fig 3), intermixed with a small amount of fibrous stroma, as observed by Masson trichrome stain (data not shown). Neoplastic cells had indistinct cell borders; moderate amounts of pale eosinophilic cytoplasm; large, central, oval to round vesicular nuclei with finely stippled chromatin; and multiple, prominent nucleoli. The mitotic index was high, with up to 14-16 mitoses, which were often atypical, per high-power field. There were scattered apoptotic cells, few binucleate cells, and multifocal areas of necrosis within the mass. Moderate numbers of heterophils and multifocal aggregates of lymphocytes infiltrated the mass. Neoplastic cells were negative for actin, desmin, von Willebrand factor, and cytokeratin, while they were diffusely immunoreactive for vimentin (Fig 4). All the antibodies tested cross-reacted with positive controls (chicken, canary, and canine skin). Electron microscopic examination revealed irregular, spindle-shaped, plump, or stellate fibroblastic cells arranged in fascicles, with thin cytoplasmic extensions and lacking external lamina. Cells contained long, tapered, or large, irregular nuclei with prominent nucleoli. Elongated nuclei frequently showed irregular invaginations with pseudoinclusion formations. Common findings were dilated stacks of rough endoplasmic reticulum, polyribosomes, randomly distributed intermediate filaments, and rare collagen secretion granules (Fig 5). No metastases were detected in other organs and tissues. The histologic diagnosis was cloacal fibrosarcoma.
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In this report, we describe a cloacal fibrosarcoma in a canary, with the diagnosis based on the typical histologic arrangement and morphology of neoplastic cells, vimentin immunoreactivity, and ultrastructural features. In pet birds, such as parrots, most fibrosarcomas involve skin and subcutis and are commonly found on the wings or legs. (1) Intestinal fibrosarcoma with myxoid degeneration is seen in pet birds (2) but has not been described in the cloaca. In fact, in psittacine birds, papilloma is the most common cloacal neoplasm, especially in Amazon parrots and macaws, (2-7) being part of the so-called internal papillomatosis of parrots. (8) Other rare cloacal neoplasms are carcinoma (2,9) and leiomyoma/sarcoma. (2) Moreover, except for lymphosarcoma, neoplasms are very rare in canaries. (2) One of the authors (H.L.S.), who has examined tissues from numerous canaries over 32 years, has not observed a tumor similar to the one described in this report. In the case we describe, tumor origin from smooth muscle cells was ruled out because neoplastic cells were negative for actin and desmin (10) and did not show ultrastructural features typical of smooth muscle differentiation (myofilaments with focal densities, attachment plaques, plasmalemmal caveolae, external lamina). (11) The aforementioned primary antibodies were also used to rule out hemangiosarcoma (factor VIII) (12) and epithelial tumors, based on histologic features and negative reaction to cytokeratin. (2) Cloacal fibrosarcoma could have similar clinical signs with cloacal papillomas, such as tenesmus, malodorous droppings, flatulence, and blood in the stool. Although there are no reports about specific therapy for this neoplastic disease, either surgical resection or cauterization of the mass to maintain patency of the vent, similar to treatment for cloacal papilloma and adenocarcinoma, (9) can be attempted.
In the present case, the histologic, immunohistochemistry, and transmission electron microscopy findings confirmed the fibroblast as the cell of origin of the neoplasm, and morphologic features revealed the malignancy of the tumor. To our knowledge, this is the first report of a cloacal fibrosarcoma in a canary. Although malignant spindle cell tumors are uncommon, they should be included in the differential diagnosis of cloacal tumors in pet birds.
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Chiara Palmieri, DVM, PhD, Dipl ECVP, Isacco Cusinato, DVM, Giancarlo Avallone, DVM, Phi), Dipl ECVP, L. Shivaprasad, BVSc, MS, PhD, Dipl ACPV, and Leonardo Della Salda, DVM, PhD, Dipl ECVP
From the Department of Comparative Biomedical Sciences, Faculty of Veterinary Medicine, Teramo University, Piazza Aldo Moro 45, 64100, Teramo, Italy (Palmieri, Cusinato, Della Salda); the Department of Animal Pathology, Hygiene, and Veterinary Public Health (DIPAV), Facolta di Medicina Veterinaria, Universita degli Studi di Milano, Via Celoria 10, 20133 Milan, Italy (Avallone); and the California Animal Health and Food Safety Laboratory System (CAHFS), Tulare Branch, University of California, Davis, 18830 Rd 112, Tulare, CA 93274, USA (Shivaprasad).