If there is a forgiveness of debt, then the lender should issue a 1099-C. If you originally financed the property with 10% down, chances are that you would still have basis more than the amount owed. It would be considered a sale and the selling price would be the debt discharged (amount on the 1099-C) and the basis would be (purchase+improvements-depreciation). You would have to go through the numbers, but you have to recognize this as a sale and use the 1099-C as your proceeds and show your gain or loss on your schedule D.
If this is a personal residence, then they may not issue one, but if they do, then you simply have the proceeds shown and the purchase price + whatever improvements you made and show a disallowed loss on the return.
Joe