AFIP Wednesday Slide Conference - No. 23

April 09 1997
Conference Moderator: Major Mark Martinez Diplomate, ACVP
U.S. Army Medical Research Institute of Infectious Disease
Bldg. 1425
Fort Detrick, MD 21702-5011
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Case I - 96N377 (AFIP 2550229)

Signalment: 2-day-old, female, Quarterhorse, equine.
History: Mild scours developed 24 hours prior to death, and progressed to severe colic. Then, no more feces passed. Radiograph revealed gas distended small and large intestines.
Gross Pathology: Turbid, flocculent, yellow fluid in peritoneal cavity. At least two areas (10-12 cm) of dark red to black discoloration of the small intestine with severe hemorrhage and congestion in the local mesentery. Mucosa of the affected bowel is dull, brown and roughened. Mesenteric lymph nodes are enlarged and hemorrhagic.
Laboratory Results: Neutropenia with degenerative left shift reported.

Microbiology: Clostridium perfringens isolated in heavy growth from intestine.

Contributor's Diagnosis and Comments: Acute, severe, diffuse, necrotizing enteritis.
Examined is a section of jejunum taken from the most severely affected area identified at the gross exam. In both sections, there is severe, diffuse, acute necrosis of the intestinal mucosa. Small remnants of intestinal epithelium remain, usually in the base of the intestinal crypts. The outline of the intestinal villi remains as blunted, short folds of necrotic tissue. The surface of these necrotic folds of epithelium is consistently covered by a thin dense line of bacteria. Bacteria are basophilic, long, and rod-shaped, and are aligned perpendicular to and in close contact with the tissue surface. Abundant degenerative neutrophils fill the lamina propria and the submucosa. There is marked diffuse congestion of the large and small vessels throughout the intestinal wall.
The findings in this foal are consistent with the history and clinical signs for acute bacterial enteritis and colitis with peritonitis and sepsis. Histologic picture of large gram- positive bacilli adhered in a "picket fence" fashion to the necrotic mucosa is classic for acute clostridial enteritis. The culture results confirm the identity of these organisms.
AFIP Diagnosis: Small intestine: Enteritis, necrotizing, acute, diffuse, severe, with necrotizing vasculitis, fibrin thrombi, diffuse transmural edema, and myriad mucosal adherent bacilli, Quarterhorse, equine.
Conference Note: The conference participants agreed with the contributor's diagnosis and comments.
Hemorrhagic necrotizing enteritis in newborn foals has been reported to be caused by the following Clostridium species: Clostridium perfringens type C, Clostridium perfringens type B, Clostridium sordelli, and Clostridium difficile. Culture and identification cytotoxins allows definitive diagnosis.
Clostridium perfringens is a gram-positive, spore-forming, anaerobic bacterium. The species is divided into 5 types, designated A-E, based on exotoxin production. There are four major antigenic lethal exotoxins. Alpha toxin is a lecithinase which acts on cell membranes to produce necrosis or hemolysis. Beta toxin, the most important toxin elaborated by Cl. perfringens types B and C, causes necrosis, decreases mobility of intestinal villi, and enhances bacterial attachment to the villi. Epsilon is also a necrotizing toxin which is produced as an inactive prototoxin and activated by enzymatic digestion (ex: trypsin in the intestine). Iota toxins increase the capillary permeability, and are produced as prototoxins which are activated by proteolytic enzymes in the intestine. In addition to these four major toxins, there are eight minor toxins produced by C. perfringens.
Types and toxins of Clostridium perfringens:
Toxin Alpha Beta Epsilon Iota
Type A ++ - - -
B + ++ + -
C + ++ - -
D + - ++ -
E + - - ++
++ = significant toxin; + = small amount; - = none detected
Diseases associated with the 5 types of Cl. perfringens include the following:
1. Type A - gas gangrene, food poisoning (humans), necrotic enteritis (chickens),
gastroenteritis (ferrets)
2. Type B - dysentery (lambs, calves), hemorrhagic enteritis (foals)
3. Type C - hemorrhagic enteritis (calves, lambs, foals, piglets, chickens), "struck"
4. Type D - enterotoxemia (sheep, goats, calves), focal symmetric encephalomalacia
5. Type E - rare; hemorrhagic enteritis (calves, rabbits)
The sequence of events leading clostridial overgrowth and toxin production in
neonates is not well elucidated. Because B toxin is trypsin labile, factors such as low
levels of the enzyme in young animals, trypsin inhibitors, and high toxin concentrations
may play a role in the disease process. Clostridia initially attach to the tips of the villi
and produce toxin. Toxin production results in damage to absorptive epithelial cells. The
epithelial cells degenerate and slough beginning at the villar tips and extending
progressively downward. Edema and transient leukocytosis occur in the lamina propria
followed by necrosis. After 6-8 hours, one third or more of the length of the villi is
damaged leading to an outpouring of serum, inflammatory cells and erythrocytes.
Contributor: Department of Pathology, Colorado State University, Fort Collins,
CO 80522.
1. Jones RL, et al: Hemorrhagic necrotizing enterocolitis associated with
Clostridium difficile infection in four foals. JAVMA 193(1):76-79, 1988.
2. Drolet R, et al: Necrohemorrhagic enterocolitis caused by Clostridium
perfringens type C in a foal. Can Vet J 31:449-450, 1990.
3. Jubb, KVF, Kennedy PC, Palmer N (eds): Pathology of Domestic Animals, 4th
edition. Academic Press, Inc., Philadelphia, pp. 237-247, 1993.
4. Schulman FY, Montali RJ, Hauer PJ: Gastroenteritis associated with
Clostridium perfringens type A in black-footed ferrets (Mustela nigripes). Vet Pathol
30:308-310, 1993.
5. Thomson, RG. Special Veterinary Pathology. BC Decker, Toronto, 1988, pp.
International Veterinary Pathology Slide Bank:
Laser disc frame #13894, 13895.

Case II - L33 (AFIP 2558677)

Signalment: 9-month-old female Beagle dog.
History: The lesion was an incidental finding at necropsy in a 9-month-old Beagle
dog used in a toxicology study.
Gross Pathology: Multifocal dark discoloration was found in the jejunum.
Laboratory Results: None.
Contributor's Diagnosis and Comments: Jejunum: heterotopy, gastric.
Gastric mucosa replaces intestinal mucosa multifocally. At the base of gastric
mucosa, tubular structures comparable to intestinal glands are present. The underlying
muscular wall is unchanged. In the segments of intestine adjacent to the gastric
mucosa, there is a marked increase in the number of goblet cells. In these areas, villi
are blunt and the lamina propria contains an increased number of inflammatory cells,
predominantly lymphocytes and macrophages with fewer neutrophils and plasma cells.
At the interface with gastric mucosa, there is goblet cell metaplasia of
enterocytes. This could represent an adaptive response to the peptic insult. The lack of
evidence for pre-existing mucosal or submucosal injury argues for a congenital origin
rather than being the result of a reparative or metaplastic process, from which it needs
to be differentiated.
Gastric heterotopia in the intestinal tract was reported to have an incidence
around 4% in laboratory Beagle dogs (Iwata et al.,1990). In one instance, it has been
the site of development of a gastric adenocarcinoma (Panigrahi, 1994).
AFIP Diagnosis: Jejunum: Heterotopic fundic gastric mucosa, segmental, with
goblet cell hyperplasia, and mild multifocal subacute inflammation, Beagle, canine.
Conference Note: Heterotopia of the gastric mucosa is extremely rare in
animals, having been noted in the Beagle breed and the cat. Heterotopic gastric
mucosa in Beagles has only been reported in the small intestine.
In humans, heterotopic gastric mucosa can occasionally be found in the intestinal
tract, most commonly in the duodenum, but also in the jejunum, ileum, colon, and
rectum. In most cases, the heterotopic gastric tissue is identified as an isolated finding
in the intestinal mucosa, but may be a component of more complex malformations such
as Meckel's and other small bowel diverticula, enteric duplications, and various other
congenital malformations. In dogs, heterotopic gastric mucosa has only been reported
in the jejunum.
Contributor: Laboratories PFIZER, Centre de Recherche, BP 159, Amboise
Cedex, 37401, FRANCE.
1. Iwata H, et al: Heterotopic gastric mucosa of the small intestine in laboratory
beagle dogs. Toxicol Pathol 18(3):373-379, 1990.
2. Panigrahi D, Johnson AN, Wosu NJ: Adenocarcinoma arising from gastric
heterotopia in the jejunal mucosa of a beagle dog. Vet Pathol 31(2):278-280, 1994.
3. Rest JR: Gastrointestinal anomalies in the dog - two case reports. Vet Rec
121:426-427, 1987.
4. Fenoglio-Preiser CM, Pascal R, Perzin KH: Tumors of the Intestines, Fascicle
27, Second Series, Atlas of Tumor Pathology, Armed Forces Institute of Pathology, pp.
403-405, 1990.
International Veterinary Pathology Slide Bank: None.

Case III - S123/96 (AFIP 2549001)

Signalment: 2.5-year-old female Labrador Retriever dog.
History: For four weeks, the owner noted lack of appetite. There was one
episode of opisthotonos and tonic seizures in the forelegs. The dog occasionally
pressed its head against the wall. At presentation, it had stooped movements, showed
severe tremors and was smacking its lips. At the owners request, the dog was
euthanized due to poor prognosis.
Gross Pathology: At necropsy, alterations were found in the cerebellum. A 1x1
cm2 leptomeningeal area was thickened and grey at the lateral surface of the left lobus
rostralis. The leptomeninx overlying the lobus caudalis (tuber and folium vermis,
pyramis and uvula) was also thickened and light to dark grey. There were focal
adhesions between the altered leptomeninx and dura mater. Sagittal sectioning of the
brain revealed thickening of the leptomeninx, the fissura prima, fissura praepyramidalis,
fissura secunda and fissura caudolateralis as well as in the areas of the lobus
Laboratory Results: None.
Contributor's Diagnosis and Comments: Malignant meningioma,
meningiothelial and fibroblastic type.
Histologically, there was a proliferation of mesenchymal cells in the leptomeninx.
Cellular borders of neoplastic cells were not well delineated. Nuclei were ovoid or
elongated and contained a moderate amount of chromatin. Moderate numbers of mitotic
figures were found. Two types of growth pattern were observed:
1. There were areas with loosely arranged reticular neoplastic cells growing in
whirling patterns. Cells were embedded in unbounded matrix and few collagen fibers.
These areas contained numerous small blood vessels which stained positively for factor-
VIII-related antigen. There were also numerous melanin-containing cells.

2. Other areas were more cellular. The bundles of fibroblastic cells were
embedded in a densely collagenous matrix.
The neoplastic cells infiltrated into the parenchyma along the spaces of Virchow
Robin and caused multifocal destruction of the grey and white matter of the cerebellum.
By immunohistochemistry, neoplastic cells were positive for vimentin and negative for
glial fibrillary acidic protein (GFAP). There were regional differences in the percentage
of neoplastic cells that expressed vimentin.
Canine meningiomas are quite common. Most of the features described in the
presented case are characteristic for the canine meningiomas. They occur
predominantly in mature and aged dogs, with a higher prevalence in females. In dogs,
they are more common in the brain than in the spinal cord. The intracranial
meningiomas have favored localizations. They occur over the convexities, in the midline
attached to the falx cerebri, below the brain stem, attached to the tentorium cerebelli or
at an intraventricular localization associated with the choroid plexus. As observed in this
case, meningiomas are regularly attached to the dura mater. Their attachment to the
dura or leptomeninges may be broad, narrow or total (meningioma en plaque).
Meningiomas show a high degree of histopathological diversity with both mesenchymal
and epithelial patterns. The range of patterns in canine meningiomas includes:
1. Meningiothelial or syncytial forms
2. Fibroblastic form
3. Transitional for (syncytial and fibroblastic)
4. Angioblastic form
5. Psammomatous form
6. Microcystic form
Mixtures of the various forms are common. Canine meningiomas commonly express
vimentin intermediate filaments. Vimentin expression is important for the differentiation
from other intracranial tumors.
The histological pattern seems to be of little prognostic importance. Most
meningiomas are benign. Presence of mitotic figures and brain invasion, as observed in
this case, as well as areas of tumor necrosis are considered as indicators of a poor
A differential diagnosis is primary sarcoma of the meninges.
AFIP Diagnosis: Brain, cerebellum: Malignant meningioma, pigmented,
Labrador Retriever, canine.
Conference Note: The presence of scattered melanin containing cells within the
neoplasm generated considerable discussion among the conference participants and
complicated determination of the diagnosis. Pigmented meningioma has not been
reported in animals. In humans, pigmented meningiomas have been reported in the
past; however, recent immunohistochemical and ultrastructural studies have shown
these tumors to be melanocytic. The existance of true melanotic meningioma has been
questioned. Primary melanocytic neoplasms of the meninges are recognized in humans
and animals. In the present case, pigmented malignant meningioma and meningeal
malignant melanoma were included in the differential diagnosis.
To resolve the issue, tissue from the neoplasm was examined by electron
microscopy. Ultrastructurally, there is extensive interdigitation of slender cytoplasmic
processes of the neoplastic cells. Many desmosomal junctions connect the processes.
The cytoplasm contains intermediate filaments. These findings are diagnostic of
meningioma. Melanoma cells contain membrane-bound melanosomes or pre-
melanosomes and have dendritic processes but do not have interdigitating cell
processes with desmosomes. The interpretation of malignancy is based on brisk mitotic
activity, areas of patternless growth and extensive perivascular infiltration. By criteria
used in human meningiomas, this would be an atypical meningioma. Frank anaplasia
and brain invasion (as opposed to perivascular extension) are required for the diagnosis
of malignant meningioma in humans. Canine meningiomas are often more aggressive
than their human counterparts.
Contributor: Institut für Pathologie, Tieräztliche Hochschule Hannover,
Bünteweg 17, 30559 Hannover, Germany.
1. Andrews, EJ: Clinicopathological characteristics of meningiomas in dogs.
JAVMA 163:151-157, 1973.
2. Braund KG, Ribas JL: Central nervous system meningiomas. Comp
Contin Ed 8:241-248, 1986.
3. Patnaik AK, Kay WJ, Hurvitz AI: Intracranial meningioma: A comparative
pathologic study of 28 dogs. Vet Pathol 23:369-373, 1986.
4. Schulman FY, Ribas JL, Carpenter JL, Sisson AF, LeCouteur, RA: Intracranial
meningioma with pulmonary metastasis in three dogs. Vet Pathol 29:196-202, 1992.
5. Summers BA, Cummings JF, de Lahunta A: Veterinary Neuropathology, pp.
355-362. Mosby, St. Louis, USA, 1995.
6. Dardick I, et al: Handbook of diagnostic electron microscopy for pathologists-
in-training. Igaku-Shoin Medical Publishers, New York, Section 4, pp. 42-45, 1996.
7. Limas C, Tio FO. Meningeal melanocytoma ("melanotic meningioma"). Its
melanocytic origin as revealed by electron microscopy. Cancer 30:1286-94, 1972.
8. Burger PC, Scheithauer BW. "Tumors of Meningothelial Cells" and
"Melanocytic Tumors" In Tumors of the central nervous system, Atlas of tumor
pathology, Third series, Fascicle 10, Armed Forces Institute of Pathology, Washington,
DC, pp345-348, 1994.
International Veterinary Pathology Slide Bank:
Laser disc frame #237, 2548, 2549, 5143.

Case IV - CP96-5002 (AFIP 2565951)

Signalment: Magellanic penguin, 2-years-old, male.

History: Experienced some minor foot problems and, thus, was in and out of
isolation and exhibit. Placed on preventative anti-malarial and anti-fungal medications
numerous times. Appetite began decreasing on June 6, 1996 while on exhibit, put on
antibiotics and placed in isolation. Breathing was labored. Received subcutaneous
fluids, nebulized with antifungal medication and given oxygen therapy. Condition
continued to worsen. Found dead on July 2, 1996.
Gross Pathology: General appearance normal. Slightly decreased pectoral
muscle mass. Air sacs appeared normal. There was a 5mm raised, firm round nodule
on the serosal surface of the distal esophagus. The mass did not extend through the
mucosal surface. Another small brownish mass was seen on the ventral surface of the
caudal right side of the sternum. This mass was 7mm diameter, irregularly shaped,
and was easily removed from the sternum. Both lungs were extremely abnormal, with
diffuse firm nodules of varying sizes throughout the parenchyma. These masses were
solid on cut sections and yellowish internally. All other organs appeared within normal
limits. The trachea was free of any plaques or discharges.
Laboratory Results: Fungal culture yielded a culture of Rhizopus sp.
Contributor's Diagnosis and Comments: Lung, bronchointerstitial pneumonia,
necrogranulomatous, hemorrhagic, diffuse, severe, mycotic.
The lungs have severe necrosis with inflammation and hemorrhage. The
inflammation consists of epithelioid macrophages, multinucleate giant cells, and
degenerate heterophils with fewer lymphocytes and plasma cells. There is moderate
fibrosis; hemorrhage and edema are also present. There are numerous, large,
approximately 10-15 µm diameter fungal hyphae which are branching, septate, non-
dichotomous, with bulbous projections. Occasional vessels have perivascular, vascular,
and luminal fungi with inflammation.
The most likely cause of death was the combination of fungemia and sepsis. The
cultures and histologic morphology are both consistent with Rhizopus.
AFIP Diagnosis: Lung: Pneumonia, necrogranulomatous, fibrinohemorrhagic,
diffuse, severe, with necrotizing vasculitis and fungal hyphae, Magellanic penguin, avian,
etiology consistent with a mucoraceous zygomycete.
Conference Note: Penguins appear to be highly susceptible to mycotic
infections. Infections caused by Aspergillus fumigatus are the most common cause of
death in captive penguins. Rhizopus infections are rarely diagnosed in birds and, to our
knowledge, have not been reported in penguins.
The taxonomy of pathogenic Zygomycetes was discussed during the conference.
Rhizopus belongs to the Family Mucoraceae, Order Mucorales, and is the most frequent
agent of mucormycosis in animals. Mucoraceous zygomycetes tend to spread along
tissue planes and invade blood vessels, often causing thrombosis. Embolization of
intravascular hyphae leads to disseminated infection, most frequently involving the
lungs, central nervous system, kidneys, liver, gastrointestinal tract, and heart.
The hyphae of the zygomycetes are indistinquishable from each other in
histologic section; specific identification requires fungal culture or other special
Contributor: University of Miami, School of Medicine, Department of Pathology
(R-46), P.O. Box 16960, Miami, FL 33121.
1. Fowler ME (editor): Zoo and Wild Animal Medicine, second edition, W.B.
Saunders, Co., pp. 294-313, 1986.
2. Chandler FW, Watts JC: Pathologic Diagnosis of Fungal Infections, ASCP
Press, Chicago, pp. 85-95, 1987.
3. Montali RJ, Migaki G (eds): Proceedings of a symposium on the comparative
pathology of zoo animals held at the National Zoological Park, Smithsonian Institution,
Washington DC, October 2-4, 1978. pp. 277-281, 1980.
International Veterinary Pathology Slide Bank:
Laser disc frame #11074, 20547.
Lance Batey
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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