Is this cancer?

Hello, I am new to this board and am reaching out for support and to see if anyone out there can answer a few questions. My mom (age 63) went to Urgent Care 12/26/2009 and was diagnosed with pneumonia. She was put on a 5 day course of Z-pack and initially felt better. However, within 2 weeks her symptoms returned and her regular doctor put her on Cefdinir (a stronger antiobiotic). The Dr also questioned the effectiveness of the Zpack. 13 days later she recovered and went to her doctor for a repeat checks Xray (1/27/10). The doctor called that day with the results and it looks like the areas on the lungs are larger and have spread. He said her lungs sounded fine and didn't hear the normal crackling associated with pneumonia. The spot on her lung is on the upper right lobe. A CT scan was ordered took place today. Here are my questions: what else can this be besides cancer? Can it still be pneumonia? If it is, why does she feel better and the lungs look worse? Can a chest CT scan differentiate cancer from pneumonia? or will a biopsy be needed either way? I am worried sick. If anyone has any insight I really apprecaite it. I also should mention she is a former smoker. Thanks.