swift uitableviewCell repeat subviews - uitableview

Question

I have a UIButton in a uitableviewcell associated to a target:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = self.tableView.dequeueReusableCellWithIdentifier("Cell") as! ProCell
cell.btn.tag = indexPath.row
cell.btn.addTarget(self, action: "buttonClicked:", forControlEvents: UIControlEvents.TouchUpInside)
return cell
}
This is the buttonClicked function:
func buttonClicked(sender:UIButton) {
let boton = sender as UIButton
let index = boton.tag
let buttonPosition: CGPoint = boton.convertPoint(CGPointZero, toView: self.tableView)
var indexPath: NSIndexPath = self.tableView.indexPathForRowAtPoint(buttonPosition)!
let cell = self.tableView.cellForRowAtIndexPath(indexPath) as! ProductoCell
cell.btn.setImage(UIImage (named: "rotacion-Null"), forState: UIControlState.Normal)
let indicador = UIActivityIndicatorView()
indicador.frame = CGRect(x: 0, y: 0, width: 25, height: 25)
indicador.color = UIColor(red: 153.0/255.0, green: 0.0, blue: 0.0, alpha: 1.0)
indicador.startAnimating()
cell.btn.addSubview(indicador)
dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {
let datosEd = ed.search(product)
dispatch_async(dispatch_get_main_queue(), {
//update UI in main thread once the loading is completed.
indicador.stopAnimating()
indicador.hidesWhenStopped = true
let label2 = UILabel(frame: CGRect(x: 15 , y: -5, width: 16, height: 16))
label2.textAlignment = NSTextAlignment.Center
label2.font = UIFont.boldSystemFontOfSize(13.0)
label2.backgroundColor = UIColor (red: 0.85, green: 0.20, blue: 0.33, alpha: 1.0)
label2.textColor = UIColor.whiteColor()
label2.layer.masksToBounds = true
label2.layer.cornerRadius = 8
let rowData = datosEd[0] as! NSDictionary
if rowData["art"] as! String == "No Results" {
label2.text = "0"
cell.contentView.addSubview(label2)
cell.btn.setImage(UIImage (named: "ed-25G"), forState: UIControlState.Normal)
} else {
label2.text = String(datosEd.count)
cell.btn.addSubview(label2)
cell.btn.setImage(UIImage (named: "ed-25R"), forState: UIControlState.Normal)
}
});
})
}
The problem is when I scroll down and scroll up back again, the subview(label2) is repeated in some cells.
Reading some responses think it has to do with the reuse of the cells, but I do not how to make the subviews are not repeated.
Some help, please... :-)