AFIP Wednesday Slide Conference - No. 9
3 November 1999

Conference Moderator:
Dr. John Pletcher, Diplomate, ACVP
Pathology Associates International
15 Worman's Mill Court
Frederick, MD 21701
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Case I 98-0712 (AFIP# 2677999)
Signalment: Six-month-old CD1xC57Bl/6 female mouse.
History: This female mouse presented with a severely distended abdomen. The investigators suspected she might have hepatic pathology (tumor, cirrhosis, or necrosis) and ascites, because this strain of mouse carries a null allele in the DcoH gene, a gene of some importance in liver function. The mouse was euthanized with CO2 and necropsied.
Gross Pathology: The only lesion was a markedly enlarged left kidney. The kidney consisted of a balloon-like structure with a transparent renal capsule, measured 4 x 2.5 x 2 cm., and was filled with slightly turbid yellow-orange fluid. A .9 x .7 x .7 cm pale tan, irregular sessile mass protruded into the lumen from the area identified as the renal pelvis.
Case 9-1. A) Distended abdomen. B) Within the left upper quadrant there is a 2.5x3.5cm cystic brown-pink mass. C) The left kidney is replaced by a (now ruptured) thin walled cystic structure with a multilobular, sessile, white mass extending from the wall.
Laboratory Results:
A direct Gram stain of the fluid from the kidney revealed no bacteria, and 4+ large amorphous crystals. There was no aerobic growth after 5 days.
Contributor's Diagnoses and Comments: Left kidney, pelvis: Carcinoma, transitional cell (primary differential), with glandular metaplasia.
Severe hydronephrosis and marked chronic active pyelitis.
Located within the renal pelvis, an irregular sessile, somewhat papillary mass projects into the large cystic space in this severely hydronephrotic kidney. The mass is incompletely covered by bilayered to pseudostratified, relatively well differentiated cuboidal epithelium (transitional epithelium), yet there is extensive down growth and stromal invasion by poorly differentiated epithelial cells forming nests, gland-like, and pseudo-tubular structures within the body of the mass. There is mild to moderate nuclear pleomorphism and a low mitotic index. The variably dense fibrous stroma contains high numbers of inflammatory cells including neutrophils, plasma cells (some with Russell bodies), eosinophils, lymphocytes and hemosiderin-laden macrophages. The remaining renal parenchyma has been reduced to a thin shell of dense fibrous connective tissue, rare sclerotic glomeruli and moderate numbers of mixed inflammatory cells.
Primary renal neoplasias in mice represent less than 1% of spontaneously arising tumors. Spontaneous tumors of the renal pelvis are extremely rare. Transitional cell carcinomas of the renal pelvis, when extremely invasive and poorly differentiated, may be difficult to distinguish from renal cell carcinomas. In the mouse, urinary bladder pathology induced by certain compounds such as 4-ethylsulfonylnaphthalene-1-sulfonamide (ENS) and Benzidine may result in a range of morphologic diagnoses for the same lesion, including chronic cystitis, papillary hyperplasia, or noninvasive carcinoma, whereas 2-Acetylaminofluorene (2-AAF), is more commonly associated with the induction of renal adenomas and carcinomas, as well as carcinomas of the urinary bladder. In all studies, mice developing lesions are considerably older (1-2 yrs) than the mouse in this case (6 months). The presence of this large mass in the renal pelvis gradually obstructed urinary outflow, resulting in an extreme case of hydronephrosis and the very distended abdomen seen clinically (see gross photographs).
AFIP Diagnosis: Renal pelvis: Transitional cell carcinoma, with hydronephrosis and chronic-active inflammation, CD1xC57Bl/6 mouse, rodent.
Conference Note: Very few slides contain any remaining renal tissue, due to this fact most conference participants preferred a differential diagnosis of Transitional cell carcinoma, ovarian carcinoma, or renal cell carcinoma.

Although spontaneous neoplasia of the renal pelvis is extremely rare in mice, its characteristics of malignancy and biologic behavior are generally the same as those affecting the urinary bladder. These tumors are generally papillary, variably invasive, with pleomorphic to anaplastic cells and commonly demonstrate varying degrees of squamous metaplasia.
Contributor: Department of Comparative Medicine, Stanford University School of Medicine, Quad 7, Bldg 330, Stanford, CA 94305-5410
1. Boorman GA, Wood M, Fukushima S: Tumours of the urinary bladder. In: Pathology of Tumours in Laboratory Animals, Vol. II, Tumours of the Mouse. pp. 383-406. IARC, France, 1994
2. Frith CH, Terracini B, Turusov VS. Tumors of the kidney, renal pelvis and ureter. In: Pathology of Tumours in Laboratory Animals Vol. II Tumours of the Mouse, pp. 357-381. IARC, France, 1994
3. Frith CH, Farmer JH, Greenman DL: Biologic and morphologic characteristics of urinary bladder neoplasms induced in BALB/c female mice with 2-acetylaminofluorene. Journ of Enviro Pathol and Tox, 3:103-119, 1979
4. Frith CH: Report of a workshop on urothelial lesions in mice. Journ of Enviro Pathol and Tox, 1:617-626, 1978
5. Shinohara Y, Frith CH: Morphologic characteristics of benign and malignant renal cell tumors in control and 2-Acetylaminofluorene-treated BALB/c female mice. Amer Journ of Pathol, 100:455-468, 1980
Case II Case 1 (AFIP 2505896)
Signalment: 54-week-old female CD-1 VAF mouse.
History: This control mouse was killed in extremis during week 48 of a two-year carcinogenicity study. It was housed in an environmentally controlled room and was fed a certified rodent chow ad libitum.
Gross Pathology: The liver was enlarged and contained multiple raised 0.5-1.0 cm diameter nodules in all lobes. The uterus contained a tan 1.0-2.0 cm diameter mass in the left uterine horn.
Contributor's Diagnoses and Comments: Liver: Histiocytic sarcoma.
Diffusely, liver sinusoids are infiltrated by round to fusiform neoplastic cells that randomly from irregular sheets and efface the parenchyma. Cells have large round to oval nuclei and abundant eosinophilic cytoplasm. Similar neoplastic proliferations were present in the uterus, cervix, bone marrow, skin (ventral abdomen), lung, mesenteric lymph node, right adrenal, meningeal vessels, colonic serosa, and mesenteric fat.
This neoplasm has also been referred to as reticulum cell sarcoma type A, malignant lymphoma (histiocytic type), histiocytic lymphoma, endometrial sarcoma, and malignant schwannoma. Research indicates that the cells are derived from histiocytes. Cells are positive for lysozyme, a-1 antitrypsin, Mac-2, and less commonly c-FMS. Histiocytic sarcomas are rare before 12 months of age, and are more common in females.
The liver is the most commonly affected organ in males and the uterus, vagina, and/or liver are often primary sites in females. Other organs that may be affected include spleen, lymph node, bone marrow, lung, kidney and ovaries. Metastasis to the lung is common when there is liver involvement.
AFIP Diagnosis: Liver: Histiocytic sarcoma, CD-1 VAF mouse, rodent.
Conference Note: Histiocytic sarcomas (HS) are common, highly malignant tumors in mice with an incidence of up to 22% percent in certain strains. HS are uncommon in mice younger than one year of age, and have been associated with viral etiologies. HS may be accompanied by myeloid hyperplasia in the spleen, and in some strains by hyaline droplets (accumulations of lysozyme-containing organelles) in the renal proximal tubular epithelium.
Contributor: Wyeth-Ayerst Research, 42 Ayerst Lab Rd., Chazy, NY 12921
1. Faccini JM, DP Abbott, Pautus GJJ: Hematopoietic and lymphatic systems. In: Mouse Histopathology, a glossary for use in toxicity and carcinogenicity studies, pp. 18-36. Elsevier, New York, 1990
2. Frith CH, PK Pattengasole, Ward JM: Neoplastic lesions. In: A Color Atlas of Hematopoietic Pathology of Mice, pp. 7-13. Toxicology Pathology Associates Little Rock, Arkansas, 1985
3. Frith CH, JM Ward, Chandra M: The morphology, immunohistochemistry and incidence of hematopoietic neoplasms in mice and rats. Tox Path 21(2):206-218, 1993
4. Ward JM, Sheldon W: Expression of mononuclear phagocyte antigens in histocytic sarcoma of mice. Vet Pathol 30:560-565, 1993
Case III NIAH (AFIP# 2681359)
Signalment: A three-month-old, male, dog
History: The dog was vaccinated at one month of age (the type of vaccine is unknown). The dog showed depression, coughing, tremor, eye and mucus. It was euthanized.
Gross Pathology: The subcutaneous and abdominal fat was decreased. There was a small amount of serosanguinous pleural effusion. The lungs were congested and its cut surface edematous. The thymus was severely atrophied.
Laboratory Results: No biochemical examination was performed. A spleen emulsion from the affected dog was injected into a normal dog, which subsequently developed fever and leukopenia. Isolation of canine distemper virus was unsuccessful.

Contributor's Diagnosis and Comments: Lung, pneumonia, interstitial, with intranuclear inclusion bodies and intracytoplasmic inclusion bodies, dog.
Etiology: Canine adenovirus-2 and canine distemper virus
In the lung, eosinophilic or basophilic intranuclear inclusion bodies were found in alveolar epithelial cells, alveolar macrophages, and bronchial epithelial cells. In some areas, congestion, hemorrhage, edema and infiltration of neutrophils, macrophages, lymphocytes, and plasma cells were noted, which suggested a secondary bacterial infection. Intranuclear inclusion bodies were also found in epithelial cells of gallbladder, renal tubules, pancreatic ductules and gastrointestinal tract, as well as in adrenal cortical cells and lymph node follicular dendritic cells. Immunohistochemical staining with anti-canine adenovirus-2 monoclonal antibody showed a positive reaction in some inclusion bodies.

In addition, eosinophilic intracytoplasmic inclusion bodies were found in bronchial epithelial cells, but immunohistochemical staining for canine distemper virus antigen failed to produce a positive reaction. However, electron microscopic examination revealed the typical ultrastructure of canine distemper virus-type particles as well as adenovirus particles.

This case was deduced to be a mixed infection with canine distemper virus and canine adenovirus-2. It demonstrates the importance of careful examination for infectious agents.
AFIP Diagnosis: Lung: Bronchopneumonia, proliferative and necrotizing, subacute, diffuse, moderate, with large basophilic and eosinophilic intranuclear inclusion bodies and small eosinophilic intracytoplasmic inclusion bodies, breed unspecified, canine, etiologies consistent with canine adenovirus-2 and canine distemper virus.
Conference Note: Conference participants agreed with the contributor's assessment. Large, eosinophilic to basophilic intranuclear inclusion bodies typical of canine adenovirus infection, and small, eosinophilic intranuclear and intracytoplasmic inclusion bodies consistent with those seen in cases of canine distemper are present. Small numbers of syncytial cells characteristic of canine distemper were also observed.
Pneumonias caused by canine adenovirus are most commonly found in conjunction with canine distemper virus infection or other conditions resulting in immune suppression.

Contributor: National Institute of Animal Health, Kannondai 3-1-1, Tsukuba, Ibaraki 305-0856, Japan
Case IV - 11142-98 (AFIP 2679507)
Signalment: Beaver (Castor canadensis), adult female, 35-pounds.
History: This beaver was one of six that died within a 2-week span in a southern Indiana wildlife reserve.
Gross Pathology: Fibrin-containing fluid filled the pleural and peritoneal cavities. Fibrin covered the pulmonary pleura, diaphragmatic peritoneum, and the capsules of the liver and spleen. White-yellow foci were widely disseminated throughout the liver and spleen. Similar foci were dispersed along the dilated and yellow-white mesenteric lymphatic vessels. Mesenteric lymph nodes were enlarged and firm. On section, they consisted mostly of friable, yellow-white areas. Within the uterus were three near-term fetuses. Placentas and the endometrium were dark red and edematous with scattered yellow-white foci.
Case 9-4. A) There are diffusely distributed variably sized white to tan (necrotic) foci replacing hepatic parenchyma. B) On cut section, the spleen contains multiple variably sized 2-5mm (necrotic) foci.
Laboratory Results: Francisella tularensis subsp. palaearctica (Type B) was isolated from the liver and spleen.

Contributor's Diagnoses and Comments:
1. Liver: Hepatitis, necrotizing (necrosuppurative), acute, multifocal, with thromboangiitis.
2. Spleen: Splenitis, necrotizing (necrosuppurative), acute, multifocal, with thromboangiitis.
This case is an example of tularemia in a beaver. Inflammation typical of tularemia was also identified in the placenta and mesenteric lymph nodes and lymphatic vessels. Type B Francisella tularensis (Francisella tularensis subsp. palaearctica) is distributed worldwide and primarily occurs in water-dwelling rodents. Type A Francisella tularensis (Francisella tularensis subsp. tularensis) is mostly limited to North America and infects rabbits and occasionally humans. Tularemia has also been reported in cats. Infection can be acquired directly or through vectors (e.g., tick or deerfly).
AFIP Diagnosis: Liver and spleen: Hepatitis and splenitis, necrotizing, acute, multifocal, moderate, with multifocal necrotizing vasculitis.
Conference Note: Tularemia is endemic worldwide, primarily causing disease in rodents and lagomorphs. Dermacentor and Amblyoma ticks pass the organism transstadially and transovarially, functioning as both vectors and reservoirs. Mosquitoes, fleas, horseflies, and lice can also transmit the disease, and there are numerous reports of zoonotic infections resulting from dog and cat bites. Carnivores may be infected by ingesting infected carcasses.

F. tularensis is a small, pleomorphic, heat-labile, gram-negative, facultative intracellular coccobacillus that is surrounded by a thick, lipid-rich capsule. All isolates are antigenically similar, but they are subdivided, based on virulence, epidemiological, and biochemical characteristics into three subspecies or biovars:

1. ssp. tularensis (Type A): most virulent; found in North America; associated with tick-borne tularemia in rabbits and zoonotic disease.
2. ssp. palaearctica (Type B): less virulent; found worldwide except for Australia and Antarctica; associated with waterborne disease of rodents.
3. ssp. mediasiatica: found in central Russia.
The organism usually enters the host via inoculation by arthropods, skin abrasions, or mucous membranes of the eye or oronasopharynx. It is generally accepted that the organisms are taken up by local macrophages. Intrahistiocytic replication occurs in local lymph nodes. Septicemia develops after 3-14 days, disseminating organisms to the spleen, liver, lymph nodes and bone marrow and causing the consistent necropsy finding of numerous small white foci on the surface of the liver, spleen (as depicted in the gross color transparencies submitted with this case), lymph nodes, and, less often, kidneys. In acute septicemia, an initial neutrophilia is often followed by neutropenia.
Disease susceptibility varies with species infected. Rodents and lagomorphs are most susceptible, and usually suffer fatal septicemia. Other herbivores, ruminants and birds are susceptible, but mortality is unusual. Carnivores are least susceptible, and require a large infective dose, rarely develop bacteremia, and only occasionally manifest overt disease. Differential diagnosis considered in this case included infections caused by Clostridium piliforme, Salmonella spp., Listeria monocytogenes, Toxoplasma gondii, and Yersinia spp.
Francisella tularensis can be grown in culture, but the potential risk of human infection requires extra caution. The preferred diagnostic test is serology. A four-fold rise in antibody titer between acute and convalescent serum is considered diagnostic; however, cross-reaction with Brucella antigen can occur. IFA is available. Organisms are visible on smears stained with new methylene blue.
Contributor: Animal Disease Diagnostic Laboratory, ADDL-1175, Purdue University, West Lafayette, IN 47907
1. Davidson WR, Nettles VF:. Beaver (Castor canadensis). In: Field Manual of Wildlife Diseases in the Southeastern United States. 2nd ed., pp. 230-231. Southeastern Cooperative Wildlife Disease Study. Athens, GA, 1997
2. Davidson WR, Nettles VF: Tularemia. In: Field Manual of Wildlife Diseases in the Southeastern United States. 2nd ed., pp. 235-238. Southeastern Cooperative Wildlife Disease Study. Athens, GA, 1997
3. Gliatto JM, Rae JF, McDonough PL, Dasbach JJ: Feline tularemia on Nantucket Island, Massachusetts. J Vet Diagn Invest 6:102-105,1994
4. Rohrbach BW: Tularemia. In: Zoonosis Updates. J Am Vet Med Assoc. Schaumburg, IL, 1990
5. Woods JP, Panciera RJ, Morton RJ, Lehenbauer TW: Feline tularemia. Compendium 20(4):442-457, 1998
6. Woods JP, Crystal MA, Morton RJ, Panciera RJ: Tularemia in two cats. J Am Vet Med Assoc 212(1):81-83, 1998
J Scot Estep, DVM
Captain, VC, USA
Registry of Veterinary Pathology*
Department of Veterinary Pathology
Armed Forces Institute of Pathology
(202)782-2615; DSN: 662-2615
* The American Veterinary Medical Association and the American College of Veterinary Pathologists are co-sponsors of the Registry of Veterinary Pathology. The C.L. Davis Foundation also provides substantial support for the Registry.
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