Page 165 - Canine Lameness

11.2 Diagnostic Mettods 137

(Barger et al. 2005; Ryseff and Bohn 2012). Other bone tumors that can stain positive for ALP
include chondrosarcoma and multilobular osteochondrosarcoma (MLO), but MLO typically
affects the axial skeleton. Bone biopsies are best performed with a Jamshidi needle (Powers et al.
1988; Sabattini et al. 2017). For bone lesions that are small, using fluoroscopy or performing radio-
graphs throughout the procedure is helpful to ensure the biopsies were indeed taken from the
lesion. It is best to sample the middle of a bone lesion for a biopsy and not the periphery (Powers
et al. 1988; Liptak et al. 2004).

11.2.3 Diagnostic Imaging
Radiographs of the affected region of the limb are indicated when neoplasia is suspected, particu-
larly for tumors that are fixed and poorly movable on palpation. Soft tissue tumors may show bone
invasion on radiographs and as such this technique is still indicated. Primary tumors of bone typi-
cally display lytic and proliferative changes but only one dominant feature may be present.
Particularly for the proximal humerus, it can be difficult to differentiate subtle lytic lesions from
underlying tissues, making orthogonal views mandatory for these cases (Figure 17.1). Tumors of
the synovium typically display lytic changes in the bones on “both sides” (i.e. proximal and distal)
of the joint. It can sometimes be difficult to differentiate between severe osteoarthritis, septic
arthritis, and a neoplasm of the synovium on radiographs (Figure 14.12C). Computed tomography
(CT) can be used to image the area and is more sensitive to show both soft tissue and bone changes.
Magnetic resonance is another useful imaging modality and is superior to CT for imaging soft tis-
sue tumors. It can also be used to image bone tumors, particularly when assessing the extent of the
tumor is important (Davis et al. 2002).

11.2.4 Staging
Once a diagnosis of neoplasia is suspected or confirmed, staging should be performed for any
neoplasia with metastatic potential. A complete blood count and chemistry panel are indicated to
assess overall health of the patient and can be helpful for diagnostic or prognostic purposes in
certain cases (e.g. hyperglobulinemia with multiple myeloma or alkaline phosphatase for osteosar-
coma, respectively). In general, thoracic radiograph (or CT) is recommended for all malignant
neoplasms to evaluate for pulmonary metastases. Abdominal radiographs and ultrasound should
be considered for tumors known to metastasize to intra‐abdominal lymph nodes, spleen, or liver.
Similar to the approach for diagnosing the primary tumor, FNA of these structures is generally the
next step to confirm metastatic disease. If nondiagnostic samples are obtained, biopsy samples
may need to be obtained via exploratory laparotomy/laparoscopy.
Some tumors, such as mast cell tumors and histiocytic sarcomas, are more likely to metastasize
to lymph nodes. For these tumors, any palpable lymph node draining the area from which the
tumor is arising from, even when not enlarged, should be aspirated. But even in the presence of
tumors that uncommonly metastasize to lymph nodes, aspirating the lymph nodes is still recom-
mended. A metastatic lymph node can provide a diagnosis and also have a significant impact on
the prognosis. A good example is osteosarcoma: lymph node metastasis is seen in only about 5% of
cases, but when present the median survival is only about two months (Hillers et al. 2005).
Other staging tests such as bone scintigraphy, or positron emission tomography (PET‐CT), may
be utilized based on the tumor and availability. PET‐CT is a sensitive test to diagnose metastatic
foci in both soft tissue and bone and is therefore an excellent staging modality to evaluate the entire
body with a single test (Selmic et al. 2017). However, availability of this modality is limited.