There are several groups of Toma surnames in Europe, not necessarily bearing mutual relationships. In Italy, the main group comes from Apulia (south east) and should be originally Balkanian (probably Albania). Toma surname also appears in Northern Italy (Piedmont and Veneto), partly as a result of immigration from the south, partly as 'native' families. You can check its geographical diffusion at
http://gens.labo.net