Hemangiopericytoma

Occuring exclusively in the dog, a sarcoma characterized by concentric whorls of spindle cells around capillaries.

Gross Appearance:
•Most often found over the joints of the forelimb and hindlimb
•Nodular cutaneous and subcutaneous mass
•Slow growth
•Very firm due to extensive collagen
•Or very soft and fluctuant, mimicking a lipoma
•Gray to white
•Firm or gelatinous in texture
•Borders of the tumor are ill defined
•May be multilobulated with areas of solid white tumor tissue separated by a zone of more myxomatous, softer tumor tissue

Histology:
Perivascular Whorled Pattern
•Layers of spindle to plump fusiform cells arranged in a concentric fashion around a central lumen

Storiform Pattern
•Tumor cells are arranged in short fascicles
•Give the appearance of a cartwheel pattern

Myxoid Foci
•Interspersed between more cellular areas
•Cells may vary from fusiform to stellate to epitheloid
•May be multinucleated cells with an abundant cytoplasm resembling giant cells

Epitheloid Pattern
•Cells have large vesicular nuclei
•Extensive amount of eosinophilic cytoplasm
•Indistinct cell borders
•Little collagen
•Increased mitotic activity
•Perivascular aggregates of lymphoid cells
•Necrosis within the tumor may be found

Cytology:
In center images note capillary running through cluster of neoplastic cells.

Breeds At Decreased Risk
Breed	Odds Ratio	95% Confidence Limit	Probability
Boxer	0.707	0.582 - 0.860	0.001
Miniature Poodle	0.531	0.435 - 0.649	0.001
Collie	0.530	0.369 - 0.761	0.001
Cocker Spaniel	0.517	0.437 - 0.611	0.001
Bernese Mountain Dog	0.474	0.212 - 1.063	0.060
Rottweiler	0.417	0.363 - 0.611	0.001
Scottish Terrier	0.435	0.283 - 0.670	0.001
Shih Tzu	0.405	0.291 - 0.563	0.001
Boston Terrier	0.396	0.224 - 0.701	0.001
Chesapeake Bay Retriever	0.317	0.131 - 0.765	0.004
Basset Hound	0.308	0.196 - 0.484	0.001
Chihuahua	0.287	0.143 - 0.576	0.001
Keeshond	0.272	0.129 - 0.572	0.001
Lhasa Apso	0.269	0.173 - 0.418	0.001
Standard Poodle	0.265	0.171 - 0.412	0.001
Dalmatian	0.264	0.146 - 0.478	0.001
Shar-Pei	0.223	0.111 - 0.448	0.001
Old English Sheepdog	0.221	0.110 - 0.444	0.001
Pekingese	0.211	0.079 - 0.565	0.001
Chow Chow	0.203	0.084 - 0.490	0.001
Newfoundland	0.199	0.064 - 0.620	0.001
Yorkshire Terrier	0.199	0.120 - 0.331	0.001
Toy Poodle	0.194	0.081 - 0.468	0.001
Akita	0.177	0.066 - 0.473	0.001
Dachshund	0.165	0.098 - 0.280	0.001
Saint Bernard	0.161	0.040 - 0.645	0.001
Mastiff	0.145	0.036 - 0.582	0.001
Maltese	0.115	0.037 - 0.357	0.001
Weimeraner	0.107	0.034 - 0.332	0.001
Bull Terrier	0.099	0.014 - 0.705	0.001
Bullmastiff	0.095	0.013 - 0.679	0.001
Kerry Blue Terrier	0.087	0.012 - 0.621	0.001
West Highland White Terrier	0.066	0.025 - 0.175	0.001
Bulldog	0.062	0.009 - 0.440	0.001

Sex Distribution (N=6040)

Sex

Status

Percent

Male	(45.0%)
37.0%

intact

(28.1%)

20.5

neutered

(16.9%)

16.5

Female	(55.0%)
63.0%

intact

(23.9%)

23.1

neutered

(31.1%)

39.9

(normal sex distribution)

Anatomic Location (N=5800)
Site	Percent
Forelimb	35.7
Hindlimb	28.9
Thorax	16.7
Abdomen	8.0
Head	2.7
Back	2.3
Neck	2.0
Perineum	1.6
Tail	1.2
Multiple	0.8
Scrotum	0.1