Undifferentiated Sarcoma in a Surinam Toad (Pipa pipa)

Christopher R. Gregory, Kenneth S. Latimer, Scott Hafner, Russell A. Breckwoldt

Department of Small Animal Medicine (Gregory) and Department of Veterinary Pathology (Latimer), University of Georgia College of Veterinary Medicine, Athens, GA 30602; United States Department of Agriculture (Hafner), Russell Research Building, Athens, GA 30602; Carolina Exotic Animal Hospital (Breckwoldt), Charlotte, NC 28205

Abstract: An antebrachial sarcoma in a Surinam toad exhibited histologic, immunohistologic, and transmission electron microscopic features of a neural tumor.

Keywords: Toad, Pipa pipa, Surinam toad, tumor, sarcoma, myelin figures, immunohistochemistry

Case Report

A 3-year-old, female, aquatic, Surinam toad (Pipa pipa) was housed in a 30-gallon freshwater aquarium. Proper nutrition and water quality were maintained throughout its life. A mild circumferential swelling of the left metacarpus was first noticed at approximately 2.5 years of age. The swelling progressed in size to 3 x 3 cm in a 6-month period, ultimately encompassing the entire antebrachium from the proximal radius and ulna to the proximal metacarpus (Figure 1). The animal died shortly thereafter and was submitted to the University of Georgia College of Veterinary Medicine for gross and histologic evaluation.

Figure 1.

Gross Observations and Histology

The distal left forearm was swollen and disfigured by a 3 x 3 cm, firm, nodular, subcutaneous mass. A focal ulceration, in which several pink nodules protruded, was present on the anterior metacarpus. Incision of the mass revealed a cream-white interior that completely effaced normal tissue architecture (Figure 2).

Figure 2.

On histologic examination, the mass contained a pleomorphic population of polyhedral to spindle cells (Figure 3). The cells varied in arrangement from linear bundles of fusiform cells to dense clusters of polyhedral cells enclosed within and interconnected by a thin fibrous connective tissue stroma. Nuclear morphology varied from cells with round hyperchromatic nuclei to cells with oval vesicular nuclei containing an occasional prominent nucleolus. The cytoplasm was foamy and mildly basophilic. Cytoplasmic borders were indistinct. Multifocal necrosis was present within the mass. The neoplastic cells were disrupting and replacing dermal adnexa and underlying skeletal muscle and bone. Small numbers of heterophils and an occasional mast cell were interspersed throughout the mass.

Figure 3.

Immunohistochemistry and Ultrastructure

Following immunohistochemical staining for various cell markers (Table 1), only neuron-specific enolase (NSE) antigen was detected (Figure 4). Transmission electron microscopy demonstrated numerous lamellar, osmiophilic structures (myelin figures) within the cytoplasm of the cells (Figure 5).

Figure 4	Figure 5

Discussion

Myelin figures occur when organelles degenerate and may also be observed in neural tumors. The tumor appeared to be of neural origin. The lack of detection of several neural-specific antigens (neurofilament, GFAP) suggests that the tumor is not differentiated enough to express these antigens. Another possibility is that the antibodies, validated for use with human tissues, do not react similarly in Surinam toads; however, the reactions occurred as expected with tissues from a similar aquatic anuran, a South African clawed toad (Xenopus laevis).

A common tumor in anurans is the herpesvirus-induced renal adenocarcinoma (Lucke’ tumor). Malignant lymphomas have been reported in South African clawed toads. These tumors were transmitted to unaffected clawed toads by injection of cell-free extract from the tumors, suggesting a viral etiology. Other epithelial, mesenchymal, and hematopoietic neoplasms have been described in amphibians.

Selected References

1. Balls M. Spontaneous neoplasms in amphibia: a review and description of six new cases. Cancer Research 22: 1142-1154, 1962.

2. Lymphosarcoma in the South African clawed toad, Xenopus laevis, a virus tumor. Annals of the New York Academy of Sciences 126:256-273, 1965.

3. Biology of Amphibian Tumors (Recent Results in Cancer Research, Special supplement). Mizell M (ed). Springer-Verlag, New York, 1969.

This Page Last Updated October 16, 2000

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