Topolino translates to English as "Little Mouse" and not directly as Mickey Mouse. To actually translate each word in Mickey Mouse to Italian would come out as the same thing because Mickey and Mouse both translate to the same word in the Italian language.
Topolino is the commonly used term for all things related to Mickey Mouse in Italy. On the official Disney.it website, Italians can sign up for the "Topolino Club," which is the Italian version of the Mickey Mouse club. In the club, you can read Italian Mickey Mouse comics, play games, and even purchase official "Topolino" merchandise from the store.
Instead of traveling to Italy to use the Italian name of Mickey Mouse, you can visit Walt Disney World's Epcot instead. At Epcot's Italy Pavilion, you will feel like you have been pulled right into the heart of Italy and you can showoff by using the name Topolino at one of their many restaurants or shops.
Signature names and trademarks are usually kept the same after translation, so for Italy to use Topolino instead of Mickey Mouse is significant. Normally Mickey Mouse would remain and become a part of the language like companies such as Nike and eBay, and with characters like Hulk Hogan.
The "Little Mouse" translation was also adapted to a popular car. Officially known as the Fiat Topolino, this car was created in 1937 and at the time it was the world's smallest car, deserving of the name and dedication to the famous mouse.