AFIP Wednesday Slide Conference - No. 15
January 6, 1999

Conference Moderator:
Dr. Jerrold Ward
National Cancer Institute
Fairview 201, P.O. Box B
Frederick, MD 21702-1201
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Case I - 98-005744 or 98-005745 (AFIP 2640348)
5744: Female, 21-week-old, 129 x C57Bl x EIIa-cre transgenic mouse.
5745: Male, 16-week-old, 129 x C57Bl x EIIa-cre transgenic mouse.
History: Heterozygous mice (+/-) for the acid a-glucosidase (GAA) gene were crossed to EIIa-cre transgenic mice for Cre-mediated deletion of the neo gene and exon 6 of the GAA gene. As mice aged, they had decreased body weight gain and developed clinical signs of muscle weakness. Later, older mice died.
Gross Pathology: None.
Laboratory Results: None.
Contributor's Diagnoses and Comments:
1. Heart and skeletal muscle: Degeneration, vacuolar, severe.
2. Heart and skeletal muscle: Regeneration, moderate.

Etiology: Abnormal storage of glycogen in cardiac myocytes and skeletal muscle. Condition: Glycogen Storage Disease Type II.
The periodic acid-Schiff (PAS) reaction shows that many vacuoles are PAS positive and diastase sensitive (longer diastase digestion times may have to be used). No evidence of heart failure has been seen as yet. Mice will be used as models for gene therapy.
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Case 15-1. Heart. Moderate numbers of cardiac myocytes contain large vacuoles.
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Case 15-1. Skeletal muscle. Muscle fibers have cytoplasmic vacuolation.
AFIP Diagnosis: Heart and skeletal muscle: Degeneration, vacuolar, diffuse, moderate, with multifocal regenerative changes, 129 x C57Bl x EIIa-cre transgenic mouse, rodent.

Conference Note: Glycogen is present in variable amounts in all cells where it serves as a readily available source of energy for cellular activities. In humans, several genetic disorders have been identified that result from a metabolic defect in the synthesis or degradation of glycogen. The best understood category of such derangements of glycogen metabolism are the glycogen storage diseases (glycogenoses). The glycogenoses result from a hereditary deficiency of one of the enzymes involved in the synthesis, transport, or degradation of glycogen, leading to accumulation of glycogen within cells in abnormal quantities or with an abnormal structure.
More than a dozen glycogenoses have been identified in humans, but the disorders may be broadly classified into three major subgroups based on pathophysiology and tissue locations of abnormally accumulated glycogen: hepatic forms, myopathic forms, and the glycogenoses associated with deficiency of a-glucosidase or lack of branching enzymes. The liver is an important organ in glycogen metabolism. Hepatic forms of glycogen storage disease occur when hepatic enzyme deficiencies involved in glycogen synthesis and/or degradation lead to abnormal storage of glycogen in the liver and hypoglycemia. In contrast to the liver, striated muscle primarily consumes glycogen as a source of energy. Myopathic forms of the disease result from a deficiency of enzymes involved in the glycolytic pathway that lead to impaired energy production and storage of glycogen in muscles.
The final major subgroup of the glycogenoses, those associated with either a deficiency of a-1,4-glucosidase (acid maltase) or lack of a branching enzyme, lead to glycogen storage in many organs and often early death, although milder adult forms of disease may occur. Type II glycogenosis (Pompe disease) results from deficiency of lysosomal acid maltase leading to abnormal storage of glycogen within lysosomes in all organs. In contrast to type II glycogenosis, the other forms are cytosolic and do not primarily involve lysosomes. In humans, the infantile form of Pompe disease results in cardiomegaly and rapidly progressive heart failure. In the adult form, affected individuals may die from pulmonary failure secondary to diaphragmatic weakness, though some survive into the seventh decade of life.
Type II glycogen storage disorders have been reported in several animal species including the Lapland dog (infantile form), Shorthorn cattle (both infantile and late-onset forms), Brahman cattle (late onset form only) and Japanese quail (late onset form only). The disease has also been reported in a cat and Corriedale sheep. While laboratory rodents have not been used extensively as a source of models for spontaneously occurring glycogen storage disorders, recent techniques in gene targeting and disruption in mice have increased the numbers and types of animals available for study. Slight alterations in the genetic background of mice of similar strains appear to contribute to distinct clinical phenotypes present at different ages. Mice with homozygous mutation for type II glycogen storage disorder present with several clinical and pathologic features of both the infantile and adult forms of the disease. The mice submitted by the contributor in this case have only been slightly genetically altered from homozygous mice.
Contributor: National Cancer Institute, NCI-FCRDC, Fairview 201, PO Box B, Frederick, MD 21702-1201.
1. Raben N, Nagaraju K, Lee E, Kessler P, Byrne B, Lee L, LaMarca M, King C, Ward JM, Sauer B, Plotz P: Targeted disruption of the acid a-glucosidase gene in mice causes an illness with the critical features of both infantile and adult human glycogen storage disease type II. J Biol Chem 273:19086-19092, 1998.
2. Becker, et al.: The African origin of the common mutation in African American patients with glycogen storage disease type II. Am J Hum Genet 62:991-994, 1998.
3. Jolly RD, Walkley SU: Lysosomal storage diseases of animals: An essay in comparative pathology. Vet Pathol 34:527-548, 1997.
4. Jones TC, Hunt RD, King NW: Intracellular and extracellular depositions; degenerations. In: Veterinary Pathology, 6th ed., pp. 241-245, Williams and Wilkins, Philadelphia, 1997.
5. Cotran RS, Kumar V, Collins T: Genetic disorders. In: Robbins Pathologic Basis of Disease, 6th ed., pp. 160-163, WB Saunders, Philadelphia, 1999.
Case II - No Label (AFIP 2643751)

Signalment: 18-month-old, male, Crl:CDâ(SD)Br rat (Rattus norvegicus).
History: This rat was in a control group in a two-year carcinogenicity study and was euthanized in moribund condition after approximately 16 months of treatment.

Gross Pathology: A spherical mass approximately 15 mm in diameter was found in the right seminal vesicle at necropsy.
Laboratory Results: None.
Contributor's Diagnosis and Comments: Carcinoma, scirrhous, seminal vesicle.
This neoplasm was one of two neoplasms that appeared at necropsy to arise from the seminal vesicles in this study of approximately 350 rats. These neoplasms may invade surrounding organs, making it difficult to determine if the origin is the seminal vesicle or the anterior prostate (coagulating gland). In this case, the gross findings suggested that the carcinoma arose from the seminal vesicles. This rat also had a large pituitary neoplasm that was thought to be the cause of the rat's clinical condition and sacrifice.
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Case 15-2. Seminal vesicle. The submucosa is heavily infiltrated by pleomorphic epithelial cells. Both mucosal papillary fronds and submucosa have an abundant inflammatory (neutrophilic) infiltrate.
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Case 15-2. Seminal vesicle. Pleomorphic tumor cells, which are admixed with neutrophils in the submucosa may contain multiple nuclei or variably sized vacuoles which displace the nucleus peripherally (signet ring cells).
AFIP Diagnosis: Seminal vesicle: Adenocarcinoma, Crl:CDâ(SD)Br rat, rodent.
Conference Note: Replacing most of the normal glandular parenchyma and compressing the adjacent coagulating gland is an unencapsulated, densely cellular, expansile, lobular neoplasm composed of polygonal cells arranged in nests, cords, papillary fronds, and glandular structures, separated and supported by a moderate to coarse fibrovascular stroma. Frequently, the nests and fronds of neoplastic cells are surrounded by abundant, immature, fibrous connective tissue (desmoplasia). The glandular ducts sometimes contain small amounts of amorphous, brightly eosinophilic secretory material and/or degenerate neutrophils. Neoplastic cells have variably distinct cell borders with small to moderate amounts of basophilic to amphophilic cytoplasm, and irregularly round to oval nuclei that are vesicular or have stippled chromatin, and one to three magenta nucleoli. The mitotic rate is high, and there are focally extensive areas of necrosis.
As noted by the contributor, distinguishing between adenocarcinomas of the coagulating gland and seminal vesicle may be difficult, especially when the tumor is large and involves adjacent organs. Determining the site of origin grossly is often troublesome, especially when tumors are located in the proximal part of the seminal vesicle adjacent to the dorsolateral prostate. Histologically, both tumors feature a glandular pattern with prominent stroma.
Most conference participants favored seminal vesicle as the primary site of origin, because many sections contain areas in which there appears to be transition from normal glandular epithelium of the seminal vesicle to the neoplasm, although this finding is not present in all histologic sections. Other histologic features of the tumor consistent with seminal vesicle origin include elongated fronds of basophilic epithelium, small amounts of brightly eosinophilic secretory product within glandular structures, and the scirrhous reaction. The coagulating gland contains smaller papillary projections and forms a pale, eosinophilic secretory substance compared to the seminal vesicle; the epithelium is lightly eosinophilic rather than basophilic. Tumors of the coagulating gland tend to be smaller and less schirrhous than those of the seminal vesicle.
While rats have a high incidence of spontaneous prostatic tumors, spontaneous neoplasms of the seminal vesicles are rare, with fewer than ten cases reported. Neoplasia of the seminal vesicles is rare in humans and domestic animals as well. Experimentally, neoplasia of the seminal vesicle can be induced in rats by exposure with several carcinogenic agents, including N-methylnitrosourea and irradiation. Because of the scarcity of reports of spontaneous seminal vesicle neoplasia in rats, little is known about the biological behavior of these tumors. A recent case report of a seminal vesicle adenocarcinoma in a Fischer 344 rat described a pleomorphic tumor with numerous mitoses but no observed metastases.
Contributor: Abbott Laboratories, Department of Pathology, D-469 AP13A, 100 Abbott Park Road, Abbott Park, IL 60064-3500.
1. Boorman GA, Elwell MR: Male accessory sex glands, penis, and scrotum. In: Pathology of the Fischer Rat, Boorman G, et al., eds., pp. 424-425, Academic Press, San Diego, CA, 1990.
2. Shirai T, Takahashi S, Tamano S: Preneoplasia and neoplasia of the rat male genital tract. In: Pathology of Neoplasia and Preneoplasia in Rodents, Bannasch P, Gossner W, eds., pp. 146-154, Schattauer, Stuttgart, GE, 1997.
3. Shoda T, et al.: A spontaneous seminal vesicle adenocarcinoma in an aged F344 rat. Toxicol Pathol 26:448-451, 1998.
4. Bosland MC, et al.: Proliferative lesions of the prostate and other accessory sex glands in male rats, URG-4. In: Standardized System of Nomenclature and Diagnostic Criteria Guides for Toxicological Pathology, pp. 1-10, Society for Toxicological Pathology, American Registry of Pathology, and the Armed Forces Institute of Pathology, Washington DC, 1998.
Case III - 97-000835, 97-106095, or 97-000839 (AFIP 2639847)

Signalment: 19-month-old, female mice, 129 x C57BL CYP1A2 -/- (knockout).
History: Mice are usually clinically normal.

Gross Pathology: At the glandular stomach along the junction with the forestomach there are round to elongated, raised plaques which measure 5-15 mm.
Laboratory Results: None.
Contributor's Diagnoses and Comments:
1. Gastric fundic hyperplasia and metaplasia, focal, severe.
2. Gastritis, focal, moderate.
3. Herniation of epithelial cysts, submucosa and tunica muscularis, moderate (in slide #97-106095).
Slide #98-000835 has areas in which many epithelial cells contain eosinophilic, hyaline cytoplasm; fewer similar cells are seen in slide #97-106095.
The pathogenesis of the hyperplasia and metaplasia is not known. We have found similar lesions in wild type mice (CYP1A2 +/+) on 129 and 129 x C57Bl backgrounds. The other regions of the stomach are usually normal. Similar and other types of gastric hyperplasia have been report in other knockouts and transgenic mice (see references).
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Case 15-3. Glandular Stomach. Hyperplastic zone is 3-4x as thick as adjacent normal mucosa. Some crypts are cystic. There ae both submucosal and subserosal lymphoid follicles.
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Case 15-3. Glandular stomach. Mucosal glands are occasionally cystic and diffusely hyperplastic, but uniform and well oriented to their basement membrane.
AFIP Diagnosis: Stomach, glandular: Hyperplasia, adenomatous, focally extensive, with mild multifocal lymphoplasmacytic gastritis, 129 x C57BL CYP1A2 -/- (knockout) mouse, rodent.
Conference Note: A focally extensive area of the gastric glandular mucosa at the junction with the squamous stomach is thickened five to ten times normal. This plaque-like thickening is characterized by long, arborizing papillary fronds of hyperplastic mucosa usually lined by a single layer of tall columnar epithelial cells. Scattered throughout the mucosa are variably-sized, dilated or cystic glands partially filled eosinophilic proteinaceous material occasionally admixed with mineralized debris. A mixture of parietal cell, chief cell, and mucous neck cell hyperplasia is present, and occasionally the epithelial cells pile-up several layers thick. Some sections contain gastric glands that have herniated through the tunica muscularis into the tunica serosa. Scattered within the submucosa and serosal adipose tissue there are nodular aggregates of lymphocytes and macrophages.
The contributor of this case (the conference moderator) has recently observed large, broad-based, papillary to polypoid lesions of the glandular stomach in these knock-out, transgenic mice. The lesions in the affected strains are consistently observed at the junction of the squamous and glandular stomach, begin as small, plaque-like thickenings of the glandular mucosa, and occur in mice eighteen months of age or older. The squamous portion of the stomach is usually unaffected. There is an 80% incidence rate in affected mice strains, and lesions increase in size as mice age.
In mice that are homozygous deficient for the aryl-hydrocarbon receptor (AHR), a wide variety of phenotypic alterations occur in major organ systems. Gastric mucosal hyperplasia commonly occurs in the pyloric stomach of AHR-deficient mice, and with age the lesions progress to gastric polyps. The aryl-hydrocarbon receptor is a ligand-activated transcription factor and is thought to be intimately involved in cellular proliferation, normal development, and physiologic homeostasis in several body systems. In the MT100 mouse, transforming growth factor-a (TGF-a) is overexpressed in the gastric glandular mucosa, and severe adenomatous hyperplasia of the glandular mucosa results characterized by proliferation of mucin-secreting cells and atrophy of parietal and zymogen secreting cells. The MT100 mouse strain serves as a model for the human condition known as Menetrier's disease, and the microscopic features and expression pattern of TGF-a in the gastric mucosa are similar in both. Chronic hypertrophic gastritis in dogs is an idiopathic condition which most often affects the body of the canine stomach, has similar microscopic features to Menetrier's disease, and may or may not cause clinical signs.
Conference participants briefly discussed whether this lesion represented a neoplastic or hyperplastic/metaplastic process, most agreeing that the lesion is not neoplastic. The mixture of proliferating mucous neck cells, parietal cells, and chief cells is not consistent with the clonal expansion of a single cell line expected with a neoplastic process.
Contributor: National Cancer Institute, NCI-FCRDC, Fairview 201, PO Box B, Frederick, MD 21702-1201.
1. Pineau T, et al.: Neonatal lethality associated with respiratory distress in mice lacking cytochrome P450 CYP1A2. Proc Nat Acad Sci USA 92:5134-5138, 1995.
2. Takagi H, et al.: Histochemical analysis of hyperplastic stomach of TGF-a transgenic mice. Dig Dis Sci 42:91-98, 1997.
3. Bockman DE, Sharp R, Merlino G. Regulation of terminal differentiation of zymogenic cells by transforming growth factor alpha in transgenic mice. Gastroenterology 108:447-454, 1995.
4. Sharp R, et al.: Transforming growth factor alpha disrupts the normal program of cellular differentiation in the gastric mucosa of transgenic mice. Development 121:149-161, 1995.
5. Fernandez-Salguero PM, Ward JM, Sundberg JP, Gonzalez FJ: Lesions of aryl-hydrocarbon receptor-deficient mice. Vet Pathol 34:605-614, 1997.
6. Barker IK, van Dreummel AA, Palmer N: The alimentary system. In: Pathology of Domestic Animals, Jubb KVF, Kennedy PC, Palmer N, eds., 4th ed., volume 2, page 62, Academic Press, San Diego, CA, 1993.
Case IV - C90-0013 (AFIP 2641930)
Signalment: Tissue from multiple, ten-week-old, female, CBA/CaJ mice.
History: This group of mice was thymectomized at six weeks of age and irradiated three weeks later. Seven to ten days following irradiation, several animals died unexpectedly.
Gross Pathology: Gross examination revealed shrunken spleens and irregular yellow and white foci scattered throughout the liver parenchyma.
Laboratory Results:
1. Bacterial culture: Negative
2. Serology: Sentinel mice from the involved room, which had been previously negative for antibody to murine viral pathogens, were serologically positive for mouse hepatitis virus.
Contributor's Diagnosis and Comments: Liver: Multifocal necrotizing hepatitis with syncytial giant cells.

Etiology: Mouse hepatitis virus (MHV).
Death is generally not associated with MHV infection except when the infection occurs in immunocompromised mice. Syncytial cells are commonly seen in murine coronavirus infection. A diagnosis of MHV is based on the liver lesions with syncytial giant cells and the serological analysis of the room sentinel mice.
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Case 15-4. Liver. Severe focal to coalescing necrosis is associated with inflammatory cell infiltration and syncytial giant cells.
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Case 15-4. Liver. Areas of hepatocellular necrosis are replaced by necrotic cellular debris, hemorrhage, neutrophils and occasional clusters of nuclei (hepatocyte syncytium). An adjacent hepatic vein contains endothelial cell hypertrophy and hyperplasia.
AFIP Diagnosis: Liver: Necrosis, random, multifocal to coalescing, with syncytia and mild neutrophilic inflammation, CBA/CaJ mouse, rodent.
Conference Note: Mouse hepatitis virus (MHV) is a murine coronavirus with several antigenic strains characterized by variability in virulence and tissue tropism. MHV is broadly classified into enterotropic and respiratory tropic groups, depending upon the primary target organ. Enterotropic strains tend to infect only the intestinal mucosa, and the virus is usually not disseminated to other tissues. Respiratory strains, on the other hand, are considered polytropic. The virus replicates in the nasal mucosa and spreads via lymphatics and the vascular system to the lungs where replication in pulmonary vascular endothelium occurs. Secondary viremia develops with spread to multiple organs, including the liver and brain. Most MHV strains are tropic for the respiratory system, and hepatitis is most often associated with respiratory strains of MHV.
Various factors influence both the susceptibility and clinical outcome of MHV infection, including virus strain, route of infection, diet, concurrent infections, age and immune status of mice. In immunocompromised mice, the consequences of MHV infection depend upon whether animals are infected with the respiratory or enterotropic coronaviral strain. Infection with respiratory MHV in athymic or SCID mice results in progressive, fatal, multisystemic disease with severe necrotizing lesions in the nasal mucosa, liver, brain, bone, lymphoid tissue, bone marrow, and other tissues. Compensatory splenic extramedullary hematopoiesis often results in splenomegaly. Virulent strains of respiratory MHV produce rapid death in immunodeficient mice, while infection with less virulent strains causes chronic wasting. Enterotropic MHV may cause chronic enteric disease in immunocompromised mice, but animals usually do not manifest clinically apparent disease.
Conference participants identified prominent syncytia at the periphery of necrotic foci within the liver; infrequent endothelial syncytia are present in some sections. Participants briefly discussed several potential causes for random hepatic necrosis in the mouse, including Tyzzer's disease (Clostridium piliforme), salmonellosis, and mousepox (ectromelia virus). Tyzzer's disease and salmonellosis do not have syncytial cells as a characteristic microscopic finding. If present in sections, salmonella organisms may be demonstrated by tissue Gram stains as short, Gram-negative, bacilli. Necrosis of Peyer's patches frequently occurs with enteric salmonellosis. Silver stains, such as the Warthin-Starry, best demonstrate the bacteria in Tyzzer's disease. They appear as filamentous bacilli within hepatocytes at the periphery of necrotic areas. In the liver lesions of mousepox, intracytoplasmic inclusions are evident in hepatocytes at the periphery of necrotic foci, and syncytial cells are not present. Cutaneous lesions, splenic necrosis, and necrosis of lymph nodes and Peyer's patches are often present in cases of mousepox.
Contributor: Comparative Medicine Division, St. Jude's Children Research Hospital, 332 North Lauderdale Street, Memphis, TN 38105.
1. Percy DH, Barthold SW: Mouse. In: Pathology of Laboratory Rodents and Rabbits, Barthold SW, ed., pp. 20-23, Iowa State University Press, Ames, Iowa, 1993.
2. Barthold SW: Mouse hepatitis virus infection. In: Monographs on Pathology of Laboratory Animals: Digestive System, Jones TC, Popp JA, Mohr U, eds., pp. 179-184, Springer-Verlag, Berlin, Germany, 1985.
3. Mickelsen SL, Greenlee PG: Diagnostic exercise: Vascular endothelial lesions in athymic nu/nu mice. Lab Anim Sci 48:92-94, 1998.
Ed Stevens, DVM
Captain, United States Army
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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