Can stable and new masses be cancer?

I had a ct scan done last week due to extreme rib and stomach pain.I have many lung masses of unknown origin. A byopsy was performed on the largest mass 18mm.appeared to be benign,this was last October.Pet scan showed mild activity in center of my chest and the mass that was biopsyed.Over time these masses shrunk so it was determined as inflamation (inflammation).These masses are considered stable at this time,but now I have many more that appeared on this new ct scan.All bloodtests were in normal range.No inflamation (inflammation).Only reason I went for recent scan was due to pain and changing symptoms.Could these new masses be cancer.Can old ones become cancer.

                                                                 Thanks in advance
                                                                 Lisafer67