Granulocytic Sarcoma in a Boa (Boa constrictor)

Christopher R. Gregory, Kenneth S. Latimer, Russell A. Breckwoldt, Raymond P. Campagnoli

Infectious Diseases Laboratory, Exotics Pathology Service, University of Georgia College of Veterinary Medicine, Athens, GA 30602; Carolina Exotic Animal Hospital (RAB), Charlotte, NC 28205

Key words: Boa, snake, reptile, tumor, sarcoma, myelogenous, granulocytic sarcoma, chloroma

Abstract. A 17-years-old male Boa constrictor was presented with a history of a mid-cervical swelling. Physical examination detected a ventral subcutaneous mass adjacent to the esophagus and extending from the base of the head to the base of the heart.

Case History

Wright-Leishman-stained slide preparations of a fine needle aspirate contained few cells. The majority of these cells were lysed. Scattered throughout the preparation were large cells with oval to oblong nuclei (Figure 1). The chromatin pattern was immature and an occasional nucleolus was observed. The cytoplasm was deeply basophilic with a perinuclear "halo". Other immature cells appeared to contain one or more round eosinophilic granules characteristic of immature heterophils. Also observed were vacuolated macrophages, erythrocytes, small mature lymphocytes, and mature heterophils. These cells were in a basophilic homogenous background containing cytoplasmic fragments and debris. The differential diagnosis included a lymphoid, histiocytic, or granulocytic neoplasm, as well as heterophilic granulomatous inflammation. Hematologic and biochemical data were normal. The owner requested euthanasia. A necropsy was performed and the tissues were submitted in 10% neutral buffered formalin to the Infectious Diseases Laboratory for histologic evaluation.

Figure 1.

Histology and Immunohistochemistry

Microscopically, the mass was composed of solid sheets of round cells with multiple areas of necrosis. The cells exhibited marked anisocytosis and anisokaryosis (Figure 2). Round, oval, reniform, horseshoe shaped, and irregularly shaped to bizarre nuclei were observed. Prominent (occasionally bizarre) nucleoli often were present within nuclei. The cytoplasm was basophilic and contained numerous poorly staining granules. The nuclear to cytoplasmic ratio was increased. Approximately 5 to 8 mitotic cells were observed per 50X field of view. More differentiated cells contained variable numbers of round eosinophilic granules. Also observed were scattered mature heterophils, mast cells, lymphocytes and plasma cells. The mass was observed invading adjacent skeletal muscle. The renal interstitium also contained large numbers of neoplastic cells that separated the remaining tubules. The liver and stomach were not involved. Giemsa, PAS, and Kinyoun’s acid-fast stains were negative for microorganisms. Scattered cells were positive for either CD3 (T cell marker) or BLA-36 (B cell marker). However, the majority of the neoplastic cells were negative for both lymphocyte markers (Figure 3).

Figure 2

Figure 3

Ultrastructure

Ultrathin sections of the formalin-fixed neoplasm were prepared for transmission electron microscopy. Ultrastructurally, the round cells contained double membrane-bound granules (Figure 4). A few granules were intact and appeared moderately electron-dense with a homogeneous matrix. Most of the granules had dissolution of the matrix. A few cells also had intracytoplasmic membrane whorls (myelin figures, Figure 5). Rare tumor cells also contained irregular inclusions with a parallel filamentous structure (Figure 6). The neoplasm appeared to be of hematopoietic origin and heterophilic cell lineage. The identity and significance of the filamentous inclusions were not determined. Based on the histologic, immunocytochemical, and ultrastructural findings, the final histological diagnosis was granulocytic (heterophilic) sarcoma.

Figure 4

Figure 5

Figure 6

Discussion

Granulocytic sarcomas or chloromas in mammals are extramedullary tumors composed of cells of granulocytic (usually neutrophilic) lineage. ¹ Due to the high concentration of myeloperoxidase in neutrophils, tumor surfaces exposed to air often turn green. ² These tumors may or may not be associated with a concurrent leukemia. ^1,2 Retroviral-induced myelocytomas in gallinaceous birds are similar in histologic appearance. ³ The occurrence of granulocytic sarcoma in reptiles is infrequent (personal observation), but has been reported in a King Cobra (Ophiophagus hannah). ⁴ Since heterophils do not contain myeloperoxidase, reptilian and avian granulocytic sarcomas do not turn green upon exposure to air and, therefore, should not be termed chloromas.

References

1. Paydas S, Hazar B, et al: Granulocytic sarcoma as the cause of giant abdominal mass: diagnosis by fine needle aspiration and review of the literature. Leukemia Research 24: 267-269, 2000.

2. Pathology of Domestic Animals, Vol. 3, third edition. Editors: Jubb KVF, Kennedy PC, Palmer N. Academic Press, Inc., Orlando. p. 100.

3. Diseases of Poultry, ninth edition. Editor: Calnek BW. Iowa State University Press, Ames, Iowa. pp. 412-413.

4. Stanley B: Granulocytic sarcoma in a King Cobra. Twenty-seventh Annual Southeastern Veterinary Pathology Conference, Tifton, GA, 1999.

This Page Last Updated October 16, 2000

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