OBJECTIVES: To report a case of eosinophilccystopathy associated to infiltrative transitional-cell carcinoma of the bladder in an adult.METHODS: We describe the case of a 79-year-old woman who complains of meso- and hipogastric pain sinceseveral months before, and to whom a parietal thickeningof the bladder was detected by means of abdominal CTscan during the diagnostic work up for a digestive diseaseindicated by the Internal Medicine Service. Cistoscopy con-firmed that finding, together with areas of greater endoluminal protrusion. Cold biopsy showed an inflammatory infiltrate with eosinophilic component. Transurethral resectionwas indicated.RESULTS: The pathological assessment was compatible withhigh-grade infiltrative transitional carcinoma of the bladder.The patient developed multiple lung metastases and diedfive months after surgery.CONCLUSIONS: Reports describing the coincidence ofboth entities are infrequent. We emphasize the importanceof a correct filiation of apparently “pseudotumoral” endo-luminal lesions