Drury R. Reavill1, DVM, DABVP (Avian Practice), DACVP; Taylor Chance2, DVM, DACVP; Richard J. Montali3, DVM, DACVP, DACZM; Robert Nordhausen4, MA; Jeremy Goodman5, DVM; Robert E. Schmidt1, DVM, PhD, DACVP
1Zoo/Exotic Pathology Service, West Sacramento, CA, USA; 2Armed Forces Institute of Pathology, Washington, DC, USA; 3Johns Hopkins University, Baltimore, MD, USA; 4California Animal Health and Food Safety Laboratory System (CAHFS), Davis, CA, USA; 5Turtle Back Zoo, West Orange, NJ, USA
An unusual subcutaneous tumor was identified in three unrelated California kingsnakes (Lampropeltis getula californiae [Blainville, 1835]). Multiple tumors were located within the subcutis along the body of the snakes. All three snakes survived surgical tumor removal and were alive at follow-up examinations.
The tumors were well-circumscribed discrete, multi-lobulated, and composed of large densely packed cells with a pale eosinophilic fibrillar cytoplasm in hematoxylin and eosin (HE) sections. In two cases, cytoplasmic amphophilic globular inclusion bodies were noted. The mitotic index was low in all three cases at <1 per 10 high-power fields. A spindle cell sarcoma of neural origin was the tentative histologic diagnosis, based on HE examination and immunohistochemistry performed.
Two cases were submitted for transmission electron microscopy. The results of the first case found intracytoplasmic globular inclusions consisting of two types. One inclusion type was highly variable in size with the appearance of cell debris. The other inclusion type had variably sized patches of uniform hexagonal particles that, in areas, appeared paracrystalline. The cytoplasm of the cells in some areas was scant but did have an abundance of filaments. In the second case without evidence of cytoplasmic inclusions on HE sections, there were numerous neurosecretory granules within the cytoplasm; however, the granules contained fragmented electron-dense bodies, with the appearance of secondary lysosomes.
Although the exact classification of these unique neoplasms is still uncertain, a neural origin is suspected. The tumors do exhibit a benign growth behavior and multiple tumor development is common.