Urinary bladder mass in a dog

A 7-year-old spayed female Schnauzer dog with chronic hematuria had a soft tissue mass within the wall of the bladder. The mass was excised and, when examined histologically, was determined to be a discrete well-organized mural mass consisting of spindloid cells arranged in swirling sheets and palisades punctuated by aggregates of principally eosinophils. The overlying transitional mucosa was extensively ulcerated and focally hyperplastic and nodular with subjacent solid down growths, superficial cysts, and the extension of tubular structures deep into the submucosa. The histologic appearance of this mass is consistent with canine polypoid eosinophilic cystitis, also known as benign inflammatory fibrous polyp.