Could do with a bit more information from you about when / how long / sort of cruise style you like etc / who would be travelling etc..

Anyway, if you want something with no ports other than Italian ones, you would probably be better looking at the smaller luxury or niche lines, as the mainstream cruises that start in the large Italian ports such as Genoa or Venice will usually take in foreign ports in Croatia, Greece and Turkey (for Eastern Med) and Spain, France, Malta and possibly Tunisia (for Western Med).

Companies such as Compagnie du Pognant operate cruises taking in Naples, Trapani, Amalfi, and other Sicilian ports...

http://en.ponant.com/Our-cruises/All...e-Mezzogiorno5

There's a really handy little site www.noblewhite.co.uk which will help you do some searching for this and may provide some interesting options away from the mainstream brands.

Mark