Page 1390 - Clinical Small Animal Internal Medicine

1328 Section 11 Oncologic Disease

should be high for bony lesions where more than one ated for swelling or mass lesions. Site‐specific signs can
VetBooks.ir articular surface is involved. occur depending on the tumor location and systemic
signs such as lethargy or inappetence may occur from
paraneoplastic syndromes or simply result from pain
Epidemiology associated with the primary or metastatic tumors.

Large‐ and giant‐breed dogs are most often affected with
appendicular OSA, and a genetic component to the dis- Diagnosis
ease has long been suspected based on observed breed
predilections. It should be noted that while small‐breed A complete physical examination should be performed
dogs have a lower likelihood of developing OSA, they are in all cases. Variable degrees of swelling, pain, and insta-
more likely to develop axial OSA than their large‐breed bility may be associated with the primary tumor. Each
counterparts. patient should also be carefully assessed for any evidence
Skeletal neoplasia is much less common in the cat, of metastasis, either to bone or to local lymph nodes.
where it is infrequently reported. OSA is the most com- Complete orthopedic and neurologic examinations
mon bone tumor in cats and, while locally invasive, car- should be performed, particularly in cases of appendicu-
ries a better prognosis than canine OSA due to the lar neoplasia where amputation may be considered as
overall lower incidence of metastasis and a protracted the surgical treatment of choice. The presence of ortho-
course of disease in cats that do develop metastases. Like pedic or neurologic co‐morbidities does not preclude
dogs, appendicular OSA in cats occurs more frequently amputation, but knowledge of these is essential for plan-
than axial, but axial OSA is relatively more common ning and owner education.
compared to the distribution in dogs. Routine laboratory evaluation by means of complete
blood count, chemistry panel, and urinalysis should be
performed. These tests serve to evaluate the patient’s
Signalment systemic health prior to anesthesia, surgery, and chemo-
therapy. In addition, elevated total alkaline phosphatase
Tumors of bone and joints typically affect dogs and cats (ALP) has been shown to be associated with a worse
that are middle aged to older. A bimodal age distribution, prognosis in canine OSA.
however, has been documented for canine OSA, with The first step in attaining a bone tumor diagnosis is
two specific peaks at 1–2 years and 7–9 years of age. orthogonal view radiographs of the affected limb or
Although the vast majority of dogs with OSA fall within region. OSA has a characteristic mixed osteolytic and
the older group, a young age should not preclude consid- osteoproductive appearance, which when combined
eration of OSA as a diagnosis. with a metaphyseal location is highly suggestive of this
Large‐breed dogs are overrepresented, with breeds such disease entity (Figure 150.1). As previously mentioned,
as the Great Dane, Rottweiler, golden retriever, German particular sites are more common for OSA, are often
shepherd, greyhound, Saint Bernard, Irish wolfhound, described by the phrase “away from the elbow, towards
Scottish deerhound, borzoi, and Doberman pinscher the knee,” with the thoracic limb being more commonly
commonly diagnosed with bone tumors. No important affected. OSA does not generally cross an articular sur-
sex predilection between male and female dogs exists, but face; this trait is more characteristic of a primary joint
neutered animals are potentially at greater risk. tumor, or fungal or bacterial osteomyelitis. Metastatic
lesions are often diaphyseal and predominantly lytic,
although a spectrum of lytic versus productive disease is
History and Clinical Signs possible with OSA. When radiographs demonstrate an
uncharacteristic lesion, other diagnostics, such as cul-
Dogs with appendicular bone or joint tumors typically ture and biopsy, can be performed to obtain a definitive
present for evaluation of lameness or swelling of a limb. diagnosis. Radiographs may also be evaluated for the
In many cases, the history may be that of a chronic, pro- presence or absence of pathologic fracture.
gressive lameness that has only been partially responsive Although classic radiographic findings may be suffi-
to analgesics. An animal may also present with an acute cient to proceed with surgical treatment, many cases may
onset of severe, nonweight‐bearing lameness, sometimes benefit from presurgical confirmation of neoplasia and/
due to pathologic fracture. It is not uncommon for own- or tumor type, particularly in patients that live or have a
ers to associate the acute onset with a nontraumatic travel history to fungal endemic areas. Ultrasound‐guided
event such as running, jumping, etc. Axial lesions may go fine needle aspiration and cytologic evaluation is a rela-
longer without detection, but animals are often evalu- tively noninvasive means of obtaining a diagnosis of