In Italy, there is some regional confusion between terms. Lasagna is the word from around the Bologna area, and is the lasagna we know and love. But for some in Italy (for example, in the South), lasagna is any pasta al forno, baked pasta, not necessarily with the broad lasagna sheets. In the Veneto, lasagna is usually called pasticcio, and does not normally include tomato sauce or beef. It does have a topping of besciamella (bechamel sauce), like the Greek pastitsio. The Veneto pasticcio is often made with seasonal ingredients such as mushrooms, asparagus or radicchio. In all probability, the Greek dish derived from the Veneto dish, as the old Republic of Venice was present in Greek territories. Ironically though, the Italian word "lasagna" derives from a Greek word (via Latin).
Below we see a cook with the unlikely name of Mimmo Corcione (sounds very Neapolitan) making a typical Veneto pasticcio with sausage and radicchio. If you're already proficient at classic lasagna, you probably won't have too much trouble reproducing this, even if you don't know Italian. For those of you who do know Italian, he speaks fairly slowly and clearly. You will note that although he uses lasagna sheets that don't require pre-cooking, he does boil them beforehand. The bechamel is a requirement, and should be made with nutmeg as he does in the video. He also uses radicchio tardivo di Treviso, which I have (unfortunately) never seen in America. You can substitute the more common round radicchio you see in the markets.
Here is a list of the ingredients he uses: butter, milk, nutmeg, flour, salt (for bechamel); extra-virgin olive oil, additional butter, dry white wine, sausage, radicchio, onion, parmigiano, lasagna sheets, white pepper, breadcrumbs.