Smithwick KeenAcc # 139621

Trisha J Oura, DVM9/27/2010

Smithwick

• 10 month old MC Scottish Terrier• Chronic hematuria– Normal stream initially then dribbles of blood-

tinged urine• Otherwise normal

Smithwick• rDVM positive contrast cystogram:– Filling defect near trigone• Rule out: hematoma vs. mass

• UA: brown, cloudy, USG = 1.036– 3+ protein, 3+ blood

• Cystospin from UA: suppurative inflammation with mild epithelial dysplasia

• Hyperechoic, broad-based, mass arising from left caudoventral bladder wall

• Cystic structures along cranial margin of the mass

• DDX:– TCC (too young?)– LSA (too irregular?)– Leiomyosarcoma/-oma

(too irregular?)– Fibrosarcoma, SCC (too weird?)– OR…..

BOTRYOID RHABDOMYOSARCOMA

Botryoid Rhabdomyosarcoma• Bladder tumors in uncommon in dogs, most =

epithelial origin and malignant• Rhabdomyosarcoma = tumor of striated muscle, can

occur elsewhere (bladder, repro, skull)– Embryonal and alveolar forms occur in juveniles– Pleomorphic form occurs in adults– Arising from mucous membrane often = botryoid Botryoid = having the form of a bunch of grapes

Botryoid Rhabdomyosarcoma• But why is skeletal muscle in the bladder?

– Embryo: UB formed when mesoderm folds medially to divide cloaca (endoderm) into rectum (dorsal) and bladder (ventral)

– This division = urorectal septum = made of mesoderm

– Urinary bladder: ventral portion = endoderm, but the dorsal wall = mesoderm

– Tumors may arise from pleuripotent mesodermal cells

Botryoid Rhabdomyosarcoma• More common in larger breed, females, up to 2 yo

– Embryonal rhabdomyosarcoma = most common soft tissue neoplasia in children <15yo

• Clinical signs related to lower urinary tract • Metastases are possible

– Uncommon, later in course of disease– Peritoneal mets reported post surgical resection

• Also associated with hypertrophic osteopathy (even without pulmonary mets)

Urinary Rhabdomyosarcoma in the Literature

• 1973 = largest case series of 7 dogs• Case reports:

– Bassett, St. Bernard*, Doberman, LabX, Irish Setter, Newfoundland– Females > males– Mass in caudal UB (usually dorsal wall), +/- ureteral obstruction w/

possible hydroureter/hydronephrosis, prostatic invasion, 1 primary urethral mass

– Recurrence with surgical resection– Multiple mets: liver, lung, lymph node, musculature, peritoneum if

history of surgery!

Prognosis?• Guarded– Most are euthanized soon after diagnosis– Tumors recur unless very aggressive surgery• Only 1 case in literature with post-op chemotherapy

• Metasasis seems to occur later in disease• Humans: treatment of choice = cystectomy

with re-routing of ureters into colon, chemotherapy and radiation therapy!

Not Just for Young Big Dogs….or Bladders…

• 11 mo F Rottweiler – gingival AND UB• 1.5 yo F Bassett – oropharynx• 2yo FI Golden - retroperitoneal• 10 yo FS mixed breed – vagina• 2 yo MC cat - liver• Yearling QH – uterus• Yearling Appaloosa - vagina

What About Smithwick?

• Surgical resection of the tumor following initial abdominal ultrasound– Histopathology = consistent with botryoid

rhabdomyoscaroma with incomplete margins• Surgical revision 09/24/10

To Be Continued….