The metastatic pattern of transitional cell carcinoma in the lungs can have a variety of radiographic appearances, including
a nodular interstitial pattern, cavitated nodules, lobar interstitial or alveolar infiltrates, and multiple soft tissue nodules
(Figure 3). Additionally, hilar lymphadenopathy may be present.22,23 Suspect lesions should ideally be interpreted by a board-certified veterinary radiologist.
Figure 3. A right lateral thoracic radiograph of a 10-year-old spayed female dalmatian with urethral transitional cell carcinoma
and pulmonary metastasis in the form of soft tissue nodules evident at initial diagnosis.
On abdominal ultrasonographic examination, iliac (regional) and other abdominal (distant) lymph nodes are evaluated for lymphadenopathy
or abnormal appearance. Although less common, metastasis can occasionally be identified in visceral organs, such as the liver
or spleen. In addition, seeding from previous transabdominal needle-tract or transmural invasion of the bladder tumor can
occasionally result in metastatic dissemination in the abdomen or carcinomatosis and is identified as free fluid, serosal
thickening, or nodular lesions. Ultrasound-guided aspirates can be obtained for cytologic examination to confirm metastasis
Obtain plain radiographs in patients with lameness, bone pain, or palpable bone masses (Figure 4). When available, bone scintigraphy can also help detect early bone metastasis since it has higher sensitivity than radiography
in identifying the site of pathologic bone turnover (Figure 5).
Figure 4. A plain ventrodorsal thoracic radiograph of the left ninth, 10th, and 11th ribs of an 8-year-old female spayed Basset
hound with bladder transitional cell carcinoma. A destructive, mixed lytic and proliferative lesion is visible in the 10th
rib that was palpable on the chest wall. The results of a cytologic examination were compatible with carcinoma, and bone metastasis
was confirmed. This dog also had widespread pulmonary metastasis.
The typical location of transitional cell carcinomas in dogs, the trigone, precludes complete surgical excision in nearly
all cases. Additionally, multiple microscopic lesions are often present in the bladder. In people, this field carcinogenesis
effect is well-documented, whereby multiple sites of the bladder mucosa undergo malignant transformation simultaneously or
sequentially, subsequent to years of carcinogen exposure.24 As a result, therapy for transitional cell carcinoma can be frustrating.