Cow udder, or mammella di mucca (or zizza di vacca, etc), once appeared on many a northern Italian dinner table, most commonly in Valle d'Aosta and made into teteun. But it can also be found boiled in at least one trattoria in Milan (La Latteria, on Via San Marco 24), and elsewhere sliced and breaded.
In Florence, where some of the city's tripe sellers stew it for hours and put it in sandwiches, it's called poppa.
Images by Conan, JUI