Page 1350 - Small Animal Internal Medicine, 6th Edition

1322 PART XII Oncology

CHAPTER 81
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Selected Neoplasms in

Dogs and Cats

HEMANGIOSARCOMA IN DOGS cardiovascular system disorders for additional information).
Dogs with cutaneous or subcutaneous neoplasms are usually
Hemangiosarcomas (HSAs; hemangioendotheliomas, angio- evaluated because of a mass, which may be surrounded by
sarcomas) are malignant neoplasms that originate from the hemorrhage. Greyhounds with intramuscular HSA typically
circulating endothelial cell precursors. They occur predomi- present with a swollen and bruised rear limb; the tumor is
nantly in older dogs (8-10 years of age) and in males; German frequently in the biceps femoris or quadriceps.
Shepherd dogs and Golden Retrievers are at high risk for this Two common problems in dogs with HSA, regardless of
neoplasm. the primary location or stage, are anemia and spontaneous
The spleen, right atrium, subcutis, and retroperitoneal bleeding. The anemia is usually the result of intracavitary
space are common sites of involvement at the time of pre- bleeding, microangiopathic hemolysis (MAHA), or both,
sentation; in Greyhounds, most HSAs originate in a muscle whereas the spontaneous bleeding is usually caused by dis-
in the rear limb. Approximately 50% of the tumors originate seminated intravascular coagulation (DIC) or thrombocyto-
in the spleen, 25% in the right atrium, 13% in subcutaneous penia secondary to MAHA (see later discussion). HSA is so
tissue, 5% in the liver, 5% in the liver-spleen–right atrium, highly associated with clinical DIC (see Chapter 87) that
and 1% to 2% simultaneously in other organs (i.e., kidney, when a dog with DIC of acute onset without an obvious
urinary bladder, bone, tongue, prostate). The latter are primary cause is evaluated, HSA should be considered high
referred to as multiple tumor, undeterminable primary. In on the list of differential diagnoses.
general, the biologic behavior of this neoplasm is highly HSAs are usually associated with a wide variety of
aggressive, with most anatomic forms of the tumor infiltrat- hematologic and hemostatic abnormalities. Hematologic
ing and metastasizing early in the disease. The exceptions are abnormalities in dogs with HSA have been well charac-
primary dermal and conjunctival or third eyelid HSAs, terized and include anemia; thrombocytopenia; the pres-
which have a low metastatic potential. ence of nucleated red blood cells (RBCs), RBC fragments
(schistocytes), and acanthocytes in the blood smear; and
Clinical and Clinicopathologic Features leukocytosis with neutrophilia, a left shift, and mono-
The owners’ complaints and the clinical signs at presentation cytosis. In addition, hemostatic abnormalities are also
are usually related to the site of origin of the primary tumor; common in dogs with HSAs. However, these hematologic
to the presence or absence of metastatic lesions; and to the abnormalities are location dependent; for example, in our
development of spontaneous tumor rupture, coagulopathies, experience, anemia, thrombocytopenia, schistocytosis, and
or cardiac arrhythmias. More than half of the dogs with HSA acanthocytosis are more common in dogs with splenic, right
are evaluated because of acute collapse after spontaneous atrial, or visceral HSA than in dogs with subcutaneous or
rupture of the primary tumor or a metastatic lesion. Some dermal HSA.
episodes of collapse may stem from ventricular arrhythmias, Most dogs with HSAs evaluated at the authors’ clinics are
which are relatively common in dogs with splenic or cardiac anemic, and more than half have RBC fragmentation and
HSA. In addition, dogs with splenic HSA are often seen acanthocytosis. The pretreatment hemostasis profiles are
because of abdominal distention secondary to tumor growth normal in less than 20% of the dogs; most dogs have throm-
or hemoabdomen. bocytopenia. Approximately half of the hemostasis profiles
Dogs with cardiac HSA are usually presented for evalua- may meet three or more criteria for diagnosis of DIC.
tion of right-sided congestive heart failure (caused by cardiac Approximately 25% of these dogs can die as a result of their
tamponade) or cardiac arrhythmias (see the chapters on hemostatic abnormalities.

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