Fibrosarcoma of the urinary bladder in a cat

Abstract

Case summary: A 5-year-old female spayed domestic shorthair cat was presented with haematuria, pollakiuria and stranguria of 2 months' duration, and a firm non-painful mass in the urinary bladder was palpated. Abdominal radiographs showed thickening and irregular cranial margins of the urinary bladder wall. Abdominal ultrasound showed a vascularised mass of mixed echogenicity almost entirely occupying the urinary bladder lumen. During explorative laparotomy, the mass appeared pedunculated and was totally excised. Histopathology was characterised by infiltration of the mucosal, submucosal and muscular layers by proliferated atypical mesenchymal cells; immunochemistry confirmed the diagnosis of fibrosarcoma. The cat was discharged with normal urination 5 days after surgery. The owner declined any imaging follow-up but reported the cat to be free of any clinical signs at 16 months after surgery.

Relevance and novel information: To the best of our knowledge, this is the first case of primary fibrosarcoma of the urinary bladder in the cat. Fibrosarcoma should be included in the differential diagnosis of urinary bladder neoplasia.

Figure 1

Right lateral view of the abdomen. Note the over-distended urinary bladder, the cranial margins appear irregular and thickened (black arrow); a radiotransparent spot is notable in the middle of the urinary bladder (white arrow)

Figure 2

Abdominal ultrasound findings. Longitudinal scan after urethral catheterisation and distension with 0.9% saline solution. (a) An irregular, rounded 4.6 × 4.2 × 4 cm lesion arises from the apex and the dorsal wall of the urinary bladder. (b) The trigone and the urethra appear normal

Figure 3

(a) Gross aspect of the urinary bladder and mass during surgery: note the thickened urinary bladder wall and the presence of a pedunculated mass that was filling the urinary bladder. (b) Gross examination: the mass measured 6.0 × 4.5 × 3.2 cm, had a fibroelastic consistency and was white to pinkish in colour; the surface is characterised by the presence of erosion and haemorrhages

Figure 4

Microscopic findings. (a) Section of the urinary bladder mass characterised by a proliferation of spindle cells irregularly arranged in interwoven and concentric bundles. In the central part of the lesion a degenerative mucinous area is observed (haematoxylin and eosin, × 4). (b) High magnification of the spindle cell pattern intertwined with a minimal deposition of amorphous eosinophilic extracellular matrix; in the right upper corner, vessels of small and medium size are observed (haematoxylin and eosin, × 10)

Figure 5

Immunohistochemical staining with vimentin: note the diffuse positive staining of the cytoplasm (× 10)