Functional ectopic interstitial cell tumor in a castrated male cat.

A 12-year-old male cat that had been castrated at 6 months of age was examined to determine the cause of urine spraying of 2 years' duration. The cat had acquired physical characteristics of a sexually intact male, and its serum testosterone concentration was greater than values expected for a castrated cat. Administration of a variety of medications did not halt urine spraying. At necropsy, an interstitial cell tumor was found in a remnant of a spermatic cord.