Sarcomatoid urothelial carcinoma of the urethra with heterologous elements in a French Bulldog

Introduction Sarcomatoid differentiation and heterologous (osteosarcoma and chondrosarcoma) elements have been rarely described in renal cell carcinoma of dogs, however not in canine urothelial tumors.

Materials and Methods A 9.5-year-old, male castrated French Bulldog, who has been suffering from progressive paresis of the right hindlimb of unknown cause for 2.5 years, was presented to the veterinarian due to perianal swelling and dyschezia. An 8x6x5 cm large mass from the pelvic cavity in close proximity to the pelvic urethra was removed and submitted for pathologic examination including histology, immunohistochemistry and electron microscopy.

Results Histologically, the tumor comprised three components: 1) interlacing bundles of spindle cells with plump oval nuclei (the largest portion), 2) islands of polygonal cells with central osteoid and chondroid production and 3) superficial lining and few islands of urothelial epithelium. The tumor was immunopositive for Gata3 and SatB2. Electron microscopy revealed a variety of intercellular junctions confirming an epithelial cell population. Ultrastructurally, the other component of the tumor revealed Fibroblast-like, irregular spindle-shaped cells containing prominent profiles of rough endoplasmic reticulum, partly filled with granular material. Cells were surrounded by collagen fibers. Malignancy criteria are present in all tumor cell populations.

Conclusions The pathologic findings of this urethral tumor are consistent with the human entity of a sarcomatoid urothelial carcinoma with heterologous elements of chondrosarcoma and osteosarcoma. While in human medicine this tumor has a poor prognosis, the dog in this case was euthanized shortly after surgery due to urine leakage into the pelvic and abdominal cavities.

Publication History

Article published online:
26 June 2024