<I>Octodon Degus</I>
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Renal Transitional Cell Carcinoma and Choristoma in a Degu (Octodon degus) PATRICK A. LESTER, RPH, DVM, MS,1,* HOWARD G. RUSH, DVM, DIPLOMATE, ACLAM,1 and ROBERT E. SIGLER, DVM, PHD, DIPLOMATE, ACVP2 A 4.5-year-old female degu (Octodon degus) was minimally responsive with a poor body condition, a rough haircoat, and moderate dehydration. Blood was present around its urethral orifi ce and on the cage bedding. Laboratory analyses revealed leukocytosis with neutro- philia and anemia; hypoproteinemia and hypoalbuminemia; hyperglycemia, hyperphosphatemia, and elevated alanine aminotransferase, blood urea nitrogen, and creatinine; and hematuria and pyuria with occasional squamous and transitional epithelial cells. A urine culture was positive for coagulase-negative Staphylococcus sp. On gross necropsy, the right kidney was enlarged, cystic, and greenish-brown, with a 10-mm, hemorrhagic, granular mass extending from the renal pelvis into the cranial cortex. Only a small amount of renal cortex appeared normal. Th e urinary bladder had focal areas of hemorrhage and contained frank blood. Histologically, the papillary mass in the right renal pelvis comprised basophilic, moderately anaplastic, clustered epithelial transition cells consistent with a transitional cell carcinoma. Internally, the tumor showed squamous metaplasia and moderate multifocal interstitial fi brosis. Th e right kidney cortex contained a choristoma comprising trabecular bone, mature adipocytes, and cellular infi ltrates suggestive of osteocytes, lymphocytes, and plasma cells. Th e urinary bladder had mild to moderate, focal, hemorrhage with neutrophilic infl ammation and contained focal areas of mild transitional cell epithelial hyperplasia; these changes may have been secondary to irritation by hemorrhage in the renal pelvis. Th ere was no evidence of metastasis. Renal transitional cell tumors are rare in rodents. Th is is the fi rst report of both a renal transitional cell carcinoma and a renal choristoma in a degu. Octodon degus, commonly called the degu, is a hystricomorph Table 1. Hematology profi le of the presented degu rodent native to South America. Degus inhabit Chile and Peru over Animal Normal reference a wide variety of altitudes, ranging from the coastal regions to the presented range for degus western slopes of the Andes (2000 m) (24). Th e average adult degu × 9 a weighs approximately 200 g and has a lifespan of 3 to 5 years. Degus Total white blood cells, 10 /L 16.8 2.4–11.36 × 9 a are very social animals and typically live in small groups (7). Th ey Neutrophils, 10 /L 14.0 1.34–6.32 Lymphocytes, × 109/L 2.64 0.27–5.36 produce a unique vocal distress call to warn of danger and possess tails Monocytes, × 109/L 0.12 0.12–1.87 that tear off to prevent capture. Th e tail does not grow back. Unlike Eosinophils, × 109/L 0.09 0.0–0.34 most rodents, the degu has a diurnal behavior pattern (15). Degus Basophils, × 109/L 0.01 0.0–0.07 are active during the day and rest at night. In addition, degus show Red blood cells, total, × 1012/L 3.29a 7.07–12.64 a circadian rise in body temperature in the morning associated with Hemoglobin, g/ dL 5.1a 11.20–20.40 peak activity in the early afternoon (27). Th ese properties make the Hematocrit, % 14.2a 32.2–55.4 degu a unique animal model for studying sleep biology, chronophar- Mean corpuscular volume, fL 43.2 41.5–52.2 macology, and circadian physiology (12, 15, 27). Mean corpuscular hemoglobin, pg 15.5 14.0–18.5 Mean corpuscular hemoglobin 35.9 33.0–38.8 concentration, g/dL Case History Red cell distribution width, % 18.2 17.2–24.6 A 4.5 year-old female degu was reported to the veterinary staff for Platelet count × 109/L 250 141–448 red-stained bedding, depression, and an unkempt appearance. Th e Mean platelet volume, fL 4.1 3.6–7.6 degu came from a conventional colony that was monitored for stan- aAbnormal value. dard rodent pathogens. Th e degu was singly housed in a polycarbonate solid-bottom rat cage (Allentown Caging Equipment, Allentown, the Association for the Assessment and Accreditation of Laboratory N.J.) with corn-cob bedding (Th e Andersons, Maumee, Ohio) and Animal Care, International. was fed commercial guinea pig chow (Purina Lab Diet 5025, PMI Physical exam revealed a depressed degu in poor body condition International, Brentwood, Mo.) as a maintenance diet with ad libi- with a rough hair coat and moderate dehydration (approximately 5 tum access to water. Th e room was maintained on a 12:12-h light: to 7%). Moderate, red-orange semi-viscous vulvar–urethral discharge dark cycle and within an average ambient temperature of 22°C. Th e resembling blood was present. Auscultation of the thoracic and ab- degu was maintained in accordance with the University Committee dominal cavities was unremarkable. In light of the animal’s advanced on the Use and Care of Animals at the University of Michigan, Ani- age and the absence of physical trauma, a preliminary diagnosis of mal Welfare Act regulations, and the Guide for the Care and Use of neoplasia was made. Th e degu was sedated with 2% isofl urane, and Laboratory Animals (21). Th e University of Michigan is accredited by blood was collected via the right brachiocephalic trunk for a complete blood count and serum biochemistry analysis (Tables 1 and 2). In ad- Unit for Laboratory Animal Medicine, University of Michigan, 018 Animal Research dition urine was collected via cystocentesis. Euthanasia was performed Facility, 1150 W. Medical Center Dr., Ann Arbor, Michigan 48109-06141; Esperion with intraperitoneal pentobarbital (200 mg/kg; Beuthanasia-D, Th erapeutics, Division of Pfi zer Global Research, 3621 S. State St. 695 KMS Place, Ann Arbor, Michigan 481082 Shering-Plough Animal Health, Kenilworth, N.J.). *Corresponding author Th e complete blood count results included a leukocytosis with neu- Volume 44, No. 3 / May 2005 CONTEMPORARY TOPICS © 2005 by the American Association for Laboratory Animal Science 41 Table 2. Serum biochemical profi le of the presented degu Animal Normal reference presented range for degus Glucose, mg/dL 276a 60–125 Alanine aminotransferase, IU/L 126a 31.7–51.3 Aspartate aminotransferase, IU/L 232a 37.5–58.3 Alkaline phosphatase, IU/L 86a 60.3–81.3 Blood urea nitrogen, mg/dL 110a 9.0–31.5 Creatinine, mg/dL 0.8 0.6–2.2 Albumin, g/dL 1.8a 2.1–3.9 Protein, g/dL 3.2a 4.6–6.2 Total bilirubin, mg/dL 0.2 0.1–1.1 Calcium, mg/dL 7.9a 9.6–10.7 Phosphorous, mg/dL 10.1a 0.0–5.3 Sodium, mmol/L 146 146–152 Potassium, mmol/L 4.4a 6.8–8.9 Chloride, mmol/L 110 99–111 aAbnormal value. Figure 2. Photomicrograph of the right kidney. Transitional cell carcinoma of renal pelvis (arrowheads). A papillary mass is present in the renal pelvis with associated hemorrhage. Presence or lack of infi ltration cannot be determined. H&E stain; magnifi cation, ×10. Figure 1. Cross section of aff ected right kidney. A granular, hemorrhagic mass was found extending from the renal pelvis into the cranial cortex. trophilia and a normocytic normochromic anemia (Table 1). Serum biochemistry results (Table 2) included hypoproteinemia and hypo- albuminemia, consistent with blood loss anemia. Other noteworthy biochemical abnormalities included hyperglycemia, hyperphospha- temia, hypocalcemia, elevated liver enzymes (alanine and aspartate aminotransferases), elevated alkaline phosphatase, and increased blood Figure 3. Photomicrograph of the right kidney. Transitional cell carcinoma of urea nitrogen. Th e remaining biochemistry values were within normal the renal pelvis. Th ere is marked squamous metaplasia and moderate multifo- × limits. Th e urinalysis revealed hematuria and pyuria with occasional cal interstitial fi brosis within the tumor. H&E stain; magnifi cation, 40. squamous and transitional epithelial cells. Urine culture results were positive for coagulase-negative Staphylococcus sp. neutrophilic infl ammation, and hemorrhage of urinary transitional On gross necropsy examination, the right kidney was moderately cell epithelium and lamina propria with mild, focal, urothelial hy- enlarged (20 by 15 by 10 mm), was greenish-brown in color, and perplasia (Fig. 5). appeared cystic. Th e left kidney appeared normal and measured 15 by 10 by 10 mm. Upon cross-sectioning of the right kidney, a 10- Discussion mm, granular, hemorrhagic mass was found extending from the renal Th is is the fi rst report of both a renal transitional cell carcinoma pelvis into the cranial cortex (Fig. 1). No evidence of gross metastasis and a renal choristoma in a degu. Renal transitional cell carcinomas was observed. have been reported to occur in other species, and their occurrence is Histologic evaluation revealed a papillary mass with associated noted to be rare (2, 9, 17). In rodents, spontaneous occurring renal hemorrhage comprised of basophilic, moderately anaplastic, clustered transitional cell carcinomas occur at very low frequencies. Chandra epithelial transition cells in the right renal pelvis, consistent with a and colleagues reported a prevelance of 0.07% in Sprague-Dawley transitional cell carcinoma (Fig. 2). Within the tumor, there was (1340 male and 1329 female) and 0.09% in F-344 (530 male and marked squamous metaplasia and moderate multifocal interstitial 530 female) rats used as controls for carcinogenicity studies (4). In fi brosis (Fig. 3). In addition, a choristoma (normal cells or tissues humans, upper urinary tract transitional cell carcinomas comprise in abnormal locations) comprising trabecular bone, mature adipo- 5 to 7% of urothelial tumors and mainly arise from the renal pelvis cytes, and cellular infi ltrates suggestive of osteocytes, lymphocytes, (16). and plasma cells, was located within the right renal cortex (Fig.