A Rare Urinary Bladder Fibrosarcoma with a Cystolith in a Dog

Case description: This report describes the simultaneous occurrence of fibrosarcoma and a urolith in the urinary bladder of a 12-year-old female terrier dog that was confirmed by pathology after excisional surgery. Clinical findings: The dog had some clinical signs such as frequent urination, hematuria and dysuria with anorexia and urinary tenesmus. Radiography confirmed the presence of a cystolith that was removed by surgery. During surgery, a solitary, pedunculated and round mass that had grown from mucosal tissue to the bladder space was observed. The mass was removed by excisional surgery and its pathologic section was prepared and stained by Hematoxylin and Eosin (H&E) and Masson’s trichrome methods. Microscopic findings in the tissue of the mass such as spindle fibroblastic cells with mild to moderate cellular pleomorphism and nuclear hyperchromasia, presence of mild mitosis figures, and chronic inflammation revealed the nature of the mass as a low-grade fibrosarcoma.Treatment and outcome: The cystolith was removed during depletion of the bladder and fibrosarcoma was removed by surgery to prevent further enlargement of the tumor and occupy the bladder space. Moreover, antibiotic therapy to avoid secondary infection was performed. Post-operation monitoring of the patient showed that there was no evidence for recurrence of the tumor within 3 months after surgery. Clinical relevance: Given the findings of this report, an occurrence of bladder fibrosarcoma has non-specific clinical signs that may challenge its differential diagnosis from other urinary-tract lesions.