Page 655 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 29 Tumors of the Male Reproductive System 633

Diagnosis and Staging

VetBooks.ir Dogs that present with suspected PCA should be fully staged to
determine extent of disease and to rule out other causes of pros-
tatic disease such as benign prostatic hypertrophy (BPH), prostati-
tis, and prostatic cysts or abscesses. 155,210,211 Physical examination,
including a thorough rectal examination, should be performed
on every patient. Rectal palpation often reveals a large, firm, and
asymmetric or irregular prostate that may be painful. Sublumbar
lymphadenomegaly may be detected on rectal or abdominal palpa-
tion. A normal-sized prostate on rectal examination in a castrated
dog is considered abnormal, even if symmetric and nonpainful. A
CBC and serum chemistry profile may demonstrate anemia,
leukocytosis, hypocalcemia, elevated bone alkaline phosphatase
activity, or signs of concurrent disease. 147,148,212 Urinalysis and
culture may show pyuria, bacteriuria, dysplastic urinary epithelial
cells, and secondary urinary bacterial infection. 134,145,147,173,212,213
Three-view thoracic radiographs may show evidence of pulmonary *
metastatic disease, sternal lymphadenomegaly, or rarely metastasis
to the extrathoracic skeletal structures (ribs, scapula). 178 Abdomi-
nal radiographs may show evidence of an enlarged prostate, with
or without evidence of mineralization; periosteal reactions on
the vertebrae, femur, or pelvic bones; and/or sublumbar or retro-
peritoneal lymphadenomegaly (Fig. 29.6A, B). 147,178,214,215 It is
important to note that the presence of mineralization, particularly
in intact dogs, is not pathognomonic for neoplasia and can occur
in dogs with prostatitis, BPH, or prostatic cysts 215–217 ; however, B
neutered dogs with prostatic mineralization are highly likely to
have prostatic neoplasia and should undergo further diagnos- 0
tics. 215 If a clinical suspicion of skeletal metastasis exists, survey
radiographs or bone scintigraphy may be useful for localiza- 1
tion. 209 PCA metastases to bone most commonly have an osteo- 2
productive component, but may be osteolytic, osteoproductive,
or mixed. Contrast studies such as retrograde urethrography may 3
be useful to evaluate irregularities in the prostatic urethra or reflux 4
of contrast into a prostatic mass; however, they are not specific 5
enough to differentiate neoplasia from inflammatory or infectious
processes. 214,218 Abdominal ultrasound can be useful to further 6
evaluate the prostate, urethra, bladder, regional LNs, and cranial 7
abdominal organs. Lymphadenomegaly, echogenicity changes, x
and mineralization may be visualized on ultrasound in dogs with 8
prostatic neoplasia, although they can also be features of nonneo- 8.05cm 9
plastic diseases (see Fig. 29.6C). 214,215
Obtaining tissue samples is considered the gold standard of C S A G P R O S
diagnosis of canine prostatic neoplasia. One retrospective his-
topathologic study highlighted several different histologic pat- • Fig. 29.6 (A) Right lateral abdominal radiograph demonstrating prostatic
mineralization (white arrow), which may be a feature of benign and malig-
terns that may be important to providing an accurate diagnosis nant disease in intact dogs. (B) Right lateral abdominal radiograph of a dog
of PCA. 152 More recently, proposals for a Gleason-type grading with prostatic carcinoma with metastasis to the sublumbar lymph nodes
system have been made to provide some level of prognostica- (black arrows) and local invasion along the sacrum and ventral aspect of the
tion in dogs and to better correlate findings to prostate cancer in seventh lumbar vertebral body (star). (C) Ultrasound image of a symmetric,
men. 163–165 In human PCA, the Gleason grading system assesses yet severely enlarged prostate of heterogeneous echogenicity in a dog diag-
the architecture of biopsy sections and is used to assign a Gleason nosed with Rocky Mountain spotted fever and bacterial prostatitis. ((A and
score based on the sum of the Gleason pattern identified in the B) Images courtesy of Dr. S. Holmes, AXIS - Animal Cross-Sectional Imaging
largest area (the primary grade) and the highest grade (secondary Specialists. (C) Image courtesy Dr. D. Jimenez, University of Georgia.)
grade). 219,220 The Gleason score has been modified over time but
has maintained its reliable and robust prognostic significance; thus or biopsy via percutaneous, perineal transrectal, or surgical routes.
there is interest in adapting this type of system to dogs. 220 Risks of percutaneous biopsies, ultrasound-guided aspirates or
A definitive diagnosis of prostatic neoplasia may be garnered biopsies, and transrectal aspirates include hemorrhage, urethral
from cytology samples as well. 155,213 A number of methods may trauma, and tumor seeding 210,221–224 Cytology or histology of sus-
provide adequate samples for diagnosis, including ejaculation, pected metastatic lesions (e.g., LN) may also aid with diagnosis
traumatic catheterization, prostatic massage, prostatic wash, ultra- and offer a simpler method of diagnosis (Fig. 29.7). Histologic
sound-guided FNA cytology, impression smears during surgery, grading of PCA is not routinely performed because there is no