Page 1351 - Small Animal Internal Medicine, 6th Edition

CHAPTER 81 Selected Neoplasms in Dogs and Cats 1323

Diagnosis biochemistry profile, hemostasis screen, urinalysis, thoracic
HSAs can be diagnosed cytologically on the basis of the radiographs, abdominal ultrasonography, and echocar-
VetBooks.ir appearance of fine-needle aspirates (FNAs) or impression diography. The latter is used to identify cardiac masses and
determine the baseline fractional shortening before institut-
smears; however, the ability to identify these neoplastic cells
in cytology samples may be impaired by blood contamina-
on treatment and prognosis). As mentioned earlier, con-
tion present, given this tumor’s vascularity. When visible, ing doxorubicin-containing chemotherapy (see the section
the neoplastic cells are similar to those in other sarcomas current splenic and right atrial masses can occur in dogs
in that they are spindle-shaped or polyhedral; however, they with HSA; in a recent study <10% of dogs initially diag-
are quite large (40-50 µm), have large nuclei with a lacy nosed with splenic HSA had a right atrial mass on staging
chromatin pattern and one or more nucleoli, and a bluish echocardiography, and 30% of dogs initially diagnosed
gray, usually vacuolated cytoplasm (Fig. 81.1). Nucleated with cardiac HSA had a splenic mass on staging ultraso-
RBCs and acanthocytes/schistocytes can also be present in nography (Boston et al., 2011). The number of dogs with
FNAs of HSAs, independently of the primary site. Although concurrent right atrial masses on staging echocardiogra-
HSA cells are relatively easy to identify in tissue aspirates or phy may be falsely decreased, due to the fact that it can be
impression smears, they are extremely difficult to identify more difficult to assess for cardiac masses in the absence of
in HSA-associated effusions. The probability of establishing pericardial effusion; however, it does appear that concur-
a cytologic diagnosis of HSA after evaluating effusions is rent cardiac HSA when splenic HSA is first diagnosed is
less than 25%. An additional problem with effusions is that less common.
they frequently contain reactive mesothelial cells that may Thoracic radiographs in dogs with metastatic HSA are
resemble neoplastic cells, leading to a false-positive diagno- typically characterized by the presence of interstitial or
sis of HSA. alveolar infiltrates, as opposed to the common “cannonball”
In general, a presumptive clinical or cytologic diagnosis metastatic lesions seen with other tumors. The radiographic
of HSA should be confirmed histopathologically, if feasible. pattern may be due to true metastases, DIC and intrapul-
Because of the large size of some splenic HSAs, however, monary bleeding, or acute respiratory distress syndrome
multiple samples (from different morphologic areas) should (ARDS).
be submitted in appropriate fixative, or ideally, the entire Ultrasonography constitutes a reliable way to evaluate
spleen should be submitted for the most thorough evalua- dogs with suspected or confirmed HSA for intraabdominal
tion. Histochemically, HSA cells are positive for von Wille- disease. Neoplastic lesions appear as nodules with variable
brand factor antigen in approximately 90% of the cases, and echogenicity, ranging from anechoic to hyperechoic (Fig.
CD31, a novel marker, is positive in up to 100% of HSA cells. 81.2). Hepatic metastatic lesions can often be identified using
In practice, these are the two most routinely used histo- this imaging technique. However, the clinician should bear
chemical stains that can be beneficial to help confirm a diag- in mind that what appear to be metastatic nodules in the
nosis of HSA. liver of a dog with a splenic mass may represent regenerative
Metastatic sites can be detected radiographically, ultra- hyperplasia rather than true metastatic lesions. Contrast
sonographically, or on computed tomography (CT). The ultrasonography appears to enhance the operator’s ability to
staging diagnostics that should be considered for dogs detect hepatic metastatic nodules from HSA, but it is not
with HSA include a complete blood count (CBC), serum easily available. Therefore we recommend using caution

FIG 81.1
Cytologic features of canine hemangiosarcoma. Note the
spindle-shaped cells, with a dark, vacuolated cytoplasm,
and the fine nuclear chromatin pattern with prominent FIG 81.2
nucleolus (×1000). Ultrasonogram of an intraabdominal hemangiosarcoma.