AFIP Wednesday Slide Conference - No. 18
- 26 February 1997
- Conference Moderator: COL William Inskeep
Chairman, Department of Veterinary Pathology
Armed Forces Institute of Pathology
Washington, DC 20306-6000
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Case I - A96-64 (AFIP 2549328)
- Signalment: Adult (aged), spayed-female, domestic
long-haired, grey feline.
- History: This cat was adopted from an animal shelter
three years ago with a history of chronic renal disease. Later,
hyperthyroidism was diagnosed which was partially controlled
by Tapazole therapy. A few days before presentation, the cat
became anorexic with progressive weight loss and eventual lethargy.
Palpation revealed a large mass in the abdominal cavity and the
cat was euthanatized at owners request.
- Gross Pathology: The cat was emaciated with no subcutaneous
or intra- abdominal fat. The left thyroid gland was markedly
enlarged (3 cm by 1 cm by 1.2 cm) and the right was markedly
atrophied. A multi-lobulated, smooth, soft tissue mass was present
in the mesentery, 4.5 cm by 4 cm by 3 cm, with firm attachments
to the ileocecal junction and the pancreas. On cut surface, the
mass consisted of homogeneous, grey- white tissue that bulged
slightly from the cut surface. Some areas had small, dark, red
to black foci. The liver had numerous discrete round to oval
masses scattered throughout the parenchyma which often bulged
from the capsular surface. Most consist of soft, grey-white tissue
similar to the mesenteric mass but a few were cavitated and filled
with clotted blood or serosanguinous fluid.
- Two similar mass 4 mm and 1 cm diameter were present in the
spleen. Two small (<2mm diameter), round, soft tissue masses
were also present in the lungs. The kidneys were bilaterally
shrunken and had diffusely rough, pitted to granular cortical
- Laboratory Results: Immunohistochemistry: Sections
of the mass in the mesentery and liver were positive for antibodies
directed against vimentin, factor VIII (von Willebrand's factor)
and MIB-1 (proliferating cells marker) and negative for cytokeratin,
synaptophysin, S-100 protein, BCL-2 (associated with inhibition
of apoptosis), and desmin.
- Contributor's Diagnosis and Comments: Hemangiosarcoma,
Hemangiosarcoma, metastatic, liver.
Additional diagnoses (tissues not provided): Hemangiosarcoma,
metastatic, lung, spleen.
Adenomatous hyperplasia, thyroid gland, unilateral.
Nephritis, chronic, interstitial, diffuse, bilateral, idiopathic.
- Hemangiosarcomas are more common in dogs than cats but several
feline cases have been reported (1,2). Several cases of primary
hemangiosarcoma have been reported in the root of the mesentery
and/or mesenteric lymph nodes(1,2). Intra- abdominal hemangiosarcomas
also tend to metastasize more frequently than those in the skin.
In this case, the largest mass was found within the mesentery
and histologic sections contained clusters of lymphocytes suggesting
it may have arisen from with a mesenteric lymph node.
- Although a few blood-filled spaces lined by plump endothelial
cells projecting into the lumens were observed in some areas
of the tumors, the solid and anaplastic appearance displayed
in the majority of the masses prompted immunohistochemical analysis
to determine the cell of origin. Neoplastic cells were positive
for vimentin and factor VIII confirming a mesenchymal and vascular
endothelial cell origin, respectively. Although lymphangiosarcoma
cannot be ruled out with certainty, the presence of red blood
cells and fibrin in some of the vascular clefts and spaces is
more consistent with a hemangiosarcoma.
- AFIP Diagnosis: Liver; mesentery: Sarcoma, poorly
differentiated, Domestic Longhair, feline.
- Conference Note: Although careful consideration was
given to the contributor's diagnosis of hemangiosarcoma, the
conference participants favored the less specific diagnosis of
poorly differentiated sarcoma. In immunohistochemical stains
performed at the AFIP, neoplastic cells did not stain positively
for factor VIII-related antigen. Neoplastic cells were also negative
for lysozyme, glial fibrillary acidic protein, smooth muscle
actin, S-100 protein, desmin, and cytokeratin. Although the origin
of this neoplasm could not be determined, the differential diagnosis
includes malignant peripheral nerve sheath tumor, malignant fibrous
histiocytoma, rhabdomyosarcoma, and leiomyosarcoma. The Department
of Soft Tissue Pathology considered this an "unclassified
malignancy" and favored a sarcoma.
- Contributor: New England Regional Primate Research
Center, Harvard Medical School, P.O. Box 9102, One Pine Hill
Drive, Southborough, MA 01772.
1. Carpenter JL, Andrews LK, Holzworth J: Tumors and tumor-like
lesions. In : Holzworth J, ed. Diseases of the cat, Philadelphia:
Saunders WB Co., pp. 406-583, 1987.
- 2. Scavelli TD, Patniak AK, Mehlhaff CJ, Hayes AA: Hemangiosarcoma
in the cat: Retrospective evaluation of 31 surgical cases. J
Amer Vet Med Assoc 187:817- 819, 1985.
Case II - S-900-96 (AFIP 2549333)
- Signalment: Canine, mixed breed, spayed female, 6-years-old.
- History: The dog was presented with a vague history
of previous anterior uveitis in both eyes. At presentation, the
right eye had buphthalmia and moderate corneal edema was present.
There was iris hypopigmentation, retinal vessel attenuation,
and atrophy and cupping of the optic nerve. Both direct and consensual
pupillary light reflexes (PLR) were absent in the right eye.
Aqueous flare, slight iris hyperpigmentation, multifocal pigment
deposits on anterior lens capsule, and a normal retina were present
in the left eye. Direct PLR was normal and consensual PLR was
partial in the left eye. The intraocular pressures (IOP) were
recorded as 19 mm Hg and 7 mm Hg for the right and left eyes,
respectively. The diagnosis of anterior uveitis was made for
the left eye and glaucoma, likely secondary to previous uveitis,
was made for the right eye. The animal was treated conservatively
with medical therapy for a period of approximately three months.
The IOP of the right eye had risen to 33 mm Hg (9mm Hg, left
eye) and the owners elected enucleation of the eye.
- Gross Pathology:.The eye was generally enlarged and
the sclera was thin. Diffuse cloudy yellow staining, as a result
of Bouin's solution fixation, prevented more detailed gross evaluation.
- Laboratory Results: None.
- Contributor's Diagnosis and Comments: Retinal, scleral,
corneal, and iridial atrophy, severe, optic nerve herniation
(consistent with chronic glaucoma).
- Preiridial and postiridial fibrovascular membrane formation,
moderate to marked, with entropion uveae and focal iridociliary
- The glaucoma in this case was considered to be secondary
to filtration angle obstruction by the relatively thin, but extensive,
preiridial fibrovascular membrane. The fibrovascular membrane
in this case extends posteriorly over the inverted and adherent
iridial free margin and across the posterior face of the iris
where focal synechia have formed between the iris, fibrovascular
membrane, and ciliary processes. Although there was virtually
no uveal inflammatory cell infiltration, it is likely that the
preiridial fibrovascular membrane in this case developed as a
consequence of previous anterior uveitis. Preiridial fibrovascular
membranes have been identified in dogs, cats, horses, and cattle
and occur most often in globes with retinal detachment, ciliary
body adenomas, chronic glaucoma, and anterior uveal melanomas.
Preiridial fibrovascular membranes in human beings, known as
rubeosis iridis, occur commonly and are most often present in
patients with diabetic retinopathy, central retinal vein occlusion,
or primary intraocular neoplasia. Occurrence secondary to chronic
uveitis is also likely. Glaucoma resulting from fibrovascular
membrane formation in human beings is known as neovascular glaucoma.
- AFIP Diagnosis:
- 1. Eye, iris, ciliary body, and filtration angle: Fibrovascular
membrane, pre-iridal and post-iridal, with entropion uveae and
anterior peripheral synechiae, mixed breed, canine.
2. Eye, retina, sclera, cornea, and iris: Atrophy, diffuse, moderate.
3. Eye, lens: Cataractous change, subcapsular.
- Conference Note: The conference participants agreed
with the contributor's diagnosis and comments. A diagnosis of
optic nerve herniation was not included above because in the
sections reviewed during the conference, this structure was absent.
- Iridal fibrovascular membrane formation is probably more
common than the literature suggests. In a study by Peiffer, et
al., membrane formation was commonly found in association with
retinal detachment, chronic endophthalmitis, chronic glaucoma,
ocular melanoma, and ciliary epithelial tumors. The membranes
are often composed of a mixture of plump spindle-shaped cells,
capillaries, and collagen fibers cover that cover the surface
of the iris, or less commonly, the pectinate ligaments and ciliary
body. Lesions attributed to the presence of iridal fibrovascular
membranes can include, hyphema, eversion or inversion of the
pupillary margin, and occlusion of the pupil or filtration angle.
The pathogenesis of iridal fibrovascular membrane may be related
to production of angiogenic factors by ischemic retina, by neoplasms,
or by leukocytes involved in ocular inflammation.
Contributor: The Animal Medical Center, 510 East 62nd
Street, New York, NY, 10021.
1. Peiffer RL, Wilcock BP, Yin H: The pathogenesis and significance
of pre-iridal fibrovascular membrane in domestic animals. Vet
Pathol 27:41-45, 1990.
2. Spencer WH: Glaucoma. In: Ophthalmic Pathology, An Atlas and
Textbook. ed. Spencer WH, 3rd ed., Vol. 1, pp. 480-547, W.B.
Saunders Company, 1985.
3. Jubb KVF, Kennedy PC, Palmer N (eds): Pathology of Domestic
Animals, 4th ed., Vol. 1, pp. 441-521, Academic Press, 1992.
- International Veterinary Pathology Slide Bank:
Laser disc frame #10204, 11999, 12000, 12007, 12010, 12011,
12019, 12044, 12046, 16818.
Case III - 1453-96 (AFIP 2549334)
- Signalment: 6-year-old spayed Domestic Shorthair cat.
- History: This cat presented recently with persistent
cough and weight loss. Radiographs and ultrasound showed a large
(20 cm), cystic, complex anterior mediastinal mass and pleural
- Gross Pathology: 11 x 7 x 2 cm multi-cystic grayish
- Laboratory Results: The hematologic and biochemical
findings were within normal limits.
- Contributor's Diagnosis and Comments: Cystic thymoma
containing both epithelial and lymphocytic components with diffuse
- Post surgically the cat is doing well.
- AFIP Diagnosis: Thymus: Thymoma, cystic, with marked
mastocytosis, Domestic Shorthair, feline.
- Conference Note: The conference participants agreed
with the contributor's diagnosis.
- Thymoma is an uncommon tumor in humans and animals. These
neoplasms have been associated with myasthenia gravis, polymyositis,
myocarditis, and dermatitis. Thymomas are rarely reported in
cats. Several of the reported cases contained cysts lined by
thymic epithelial cells, most often of the fusiform type, that
were separated by prominent fibrous bands . Mast cells, which
are preseent in small numbers in the normal feline thymic medulla,
can be numerous in feline thymomas.
Thymic epithelial cells are derived from endoderm of the third
and fourth pharyngeal pouches and are the neoplastic cells in
thymoma. These cells may have round, oval, or fusiform nuclei,
and may be arranged in solid, trabecular, cribriform, whorled,
cystic, or rosette patterns. Thymomas often contain numerous
non-neoplastic lymphocytes which may obscure the true nature
of the neoplasm. In this case, thymic lymphoma must be ruled
- Normal thymic epithelial cells produce several small polypeptide
hormones including thymosin, thymopoietins, thymic humoral factor,
thymulin, and the thymostimulins. Thymulin is interesting, since
it is a zinc-containing peptide that can partially restore T
cell function in thymectomized animals. Thymic epithelial cells
also secrete IL-1.
- Contributor: The Animal Medical Center, 510 East 62nd
Street, New York, NY 10021.
1. Suster S and Rosai J: Cystic thymomas: A clinicopathologic
study of ten cases. Cancer 69:92-97. 1992.
- 2. Carpenter JL, Holzworth J: Thymoma in 11 cats. JAVMA 181(3):248-251,
3. Tizard IR (ed): Veterinary Immunology. 5th ed., W.B. Saunders,
pp. 78-80, 1996.
4. Moulton JE (ed): Tumors in Domestic Animals, 3rd ed., University
of California Press, pp. 267-268, 1990.
- 5. Holzworth J (ed): Diseases of the Cat: Medicine and Surgery,
Vol. 1, W.B. Saunders, pp. 439-441, 1987.
International Veterinary Pathology Slide Bank:
Laser disc frame #1134, 1135, 5967, 5968, 7911, 21559.
Case IV - 96:1186 (AFIP 2558107)
Signalment 26-week-old White Leghorn Dekalb XL layer chicken.
- History: During June, July and August, a chronic mortality
rate of 5-10% was identified in a 600-bird flock of layers. The
birds were lethargic and weak and had droopy combs. A mild to
moderate drop in production was noted. The mortality peaked in
August. The birds were 25 weeks of age and had been raised from
Day 1 on the farm. The layers were maintained on litter flooring
and were fed 16% layer feed. Marek's disease was diagnosed in
this flock earlier, and coccidiostats were withdrawn at 18 weeks.
- Gross Pathology: Multiple laying chickens were examined.
The small intestines were markedly dilated and contained bloody
fluid with flecks of tissue and blood clots. The serosa of the
middle one-third of the small intestine was red-grey with prominent
blood vessels. Numerous, minute, 1-2 mm, smooth foci were disseminated
across the serosa of the middle one-third of the small intestine,
and petechiae were dispersed along the associated mucosa. The
wall of the middle one-third of the small intestine was markedly
thickened. The layers were in production, and one bird had symmetrically
enlarged liver, spleen, and kidney with numerous, slightly raised,
white, parenchymal foci ranging from 1-8 mm in diameter.
- Laboratory Results: Serologic tests for antibodies
to Mycoplasma gallisepticum, Mycoplasma synoviae, avian influenza,
and Newcastle disease virus were negative. Bacterial cultures
of liver and small intestine yielded no significant growth.
- Contributor's Diagnosis and Comments: Morphologic
diagnosis: Small intestine. Marked, segmental, subacute, lymphohistiocytic
enteritis with intralesional protozoal schizonts and hemorrhage.
- Etiology: Eimeria necatrix.
- The sections are of the middle one-third of the small intestine.
Dispersed throughout the lamina propria are numerous aggregates
of closely-packed coccidian schizonts. The schizonts contain
large numbers of densely-packed, comma-shaped merozoites that
are limited by a thin membrane. In some foci, aggregates of schizonts
are surrounded by mantles of foamy macrophages and occasional
multinucleate giant cells. In other foci, mononuclear infiltrates
of large numbers of lymphocytes and macrophages with occasional
plasma cells and few eosinophils are present in the lamina propria
surrounding schizonts. Spotty proprial hemorrhage is present.
Along the mucosal surface, there is a layer of hemorrhage, fibrin,
and proteinaceous fluid within which are scattered rafts of displaced,
necrotic epithelial cells and aggregates of very large numbers
of closely-packed, comma shaped, uninucleate merozoites. There
is mild to moderate reduction and fusion of villi.
- Eimeria necatrix is a severe pathogen and can cause high
mortality in chicken flocks. Outbreaks of coccidiosis usually
occur when environmental parameters favor sporulation of oocysts;
for example, warm temperatures, wet litter, and the presence
of old carrier birds. Probably because of its comparatively low
reproductive capability, E. necatrix is not able to compete well
with other coccidia and is diagnosed mostly in older birds such
as brooder pullets or layer pullets (9 - 14 weeks or older).
Gross lesions of E. necatrix are characterized by ballooning
of the middle one-third of the small intestine with petechiae
and disseminated white foci (i.e. schizonts). The intestinal
contents are mucoid and bloody. Microscopically, large diameter
second-generation schizonts (up to 66 µm) containing hundreds
of merozoites penetrate the deep mucosa and can penetrate the
submucosa and muscularis externa. Only large diameter schizonts
and merozoites are identified in the small intestine; sexual
stages and oocysts develop in small numbers in the cecal mucosa
only and cause little pathogenic effect.
- Immunosuppressive disease may act in concert with coccidiosis
to produce more severe disease. Marek's disease may interfere
with the development of immunity to coccidiosis.
- The tissue damage resulting from proprial infiltration by
second-generation schizonts of E. necatrix may allow for subsequent
infection by Salmonella sp or Clostridium perfringens, the latter
leading to necrotic enteritis.
- AFIP Diagnosis: Small intestine: Enteritis, proliferative,
subacute, diffuse, moderate, with villar atrophy, necrosis, hemorrhage,
and coccidial schizonts, White Leghorn Dekalb XL chicken, avian.
- Conference Note: The conference participants agreed
with the contributor's diagnosis. The term "proliferative"
was added to the diagnosis because of the prominent mucosal hyperplasia.
- Eimeria necatrix has a typical eimerian life cycle. After
ingestion of an oocyst, it is crushed in the gizzard and sporozoites
are released. Sporozoites enter cells in the mucosa of the intestine
and begin the cell cycle leading to reproduction. At least two
generations of asexual reproduction, called schizogony or merogony,
lead to a sexual phase, where small, motile microgametes seek
out and unite with macrogametes. The resulting zygotes matures
into oocysts, which are released from the intestinal mucosa and
shed in the feces. This entire process takes from 4 to 6 days
depending on species. In some species such as E. necatrix and
E. tenella, maximum tissue damage occurs when second-generation
schizonts rupture to release merozoites. Characteristics useful
in identification of species of Eimeria in chickens are: 1) location
of the lesion in the small intestine; 2) gross appearance of
the lesion; 3) oocyst size; 4) size of schizonts and merozoites;
and 5) location of parasites (epithelial versus subepithelial)
in intestinal tissue sections.
- Contributor: Department of Pathology, University of
Connecticut, 61 North Eagleville Road, U-89, Storrs, CT 06269-3089
1. Biggs PM, Long Pl, Kenzy SG, and Roots DG: Investigation into
the association between Marek's disease and coccidiosis. Acta
Vet 38:65-75, 1969.
- 2. Helmbolt CF, and Bryant ES: The pathology of necrotic
enteritis in domestic fowl. Avian Dis 15:775-780, 1971.
- 3. McDougald LR, Reid WM: Coccidiosis, In: Diseases of Poultry,
9th ed., Calrek BW, Barnes HJ, Beard CW, Reid WM and Yoder HW
Jr.(eds), Iowa State University Press, Ames, Iowa. pp. 780-797,
- 4. Riddell, C: Alimentary System. In: Avian Histopathology,
1st ed. The American Association of Avian Pathologists, University
of Pennsylvania, New Bolton Center, Kennett Square, Pennsylvania.
pp. 47-56, 1987.
- 5. Whiteman CE and Bickford AA: Coccidiosis. In: Avian Disease
Manual. 2nd American Association of Avian Pathologists, University
of Pennsylvania, New Bolton Center, Kennett Square, Pennsylvania,
- International Veterinary Pathology Slide Bank:
Laser disc frame #19550.
- Lance Batey, 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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