Thanks for all valuable replies.Find in few sites there is 2% of chance for node metastasis even for below 1.5mm dept, irrespective of size of the tongue tumor and .I can guess even for half mm or 1mm there is a chance 1 or 2% to 5%.If your onco suggests neck dissection(ND) go for it. But If your onco telling you its only 1mm or below 1 mm only or superficial only or only 5%,10% low risk for node metastasis..... ask if he can guarantee that there is no cancer cells in neck nodes..definitely he will say big NO.Then all should go for ND if their primary surgery excluded neck dissection.Why take chance even it is 1% or 2% or half percent?