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

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
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