[{"_id":1,"items":[{_id:1,lastModificationBy:[]}]}]

db.collection.update({_id:1,"items._id":1},{$set:{"items.$.concept":"req.body.concept","items.$.incomeAmount":"req.body.incomeAmount","items.$.description":"req.body.description","items.$.expenseAmount":"req.body.expenseAmount"},$push:{"items.$.lastModificationBy":{"uid":1,"username":"req.user.username","comments":"req.body.comments"}}})