I had a cat scan in 2007 with & without contrast (plus 2 in 2004) that never showed a tumor... in 2010 it was already 1.6 cm. How did a slow growing tumor that I've been told that I've probably had anywhere from 8 to 16 years not show up till then....
First of all, it is much easier for a radiologist to read an MRI than a CAT scan. CAT scans are better for planning radiation treatment but are not as easy for the eye to interpret as an MRI. So a smaller AN might have gone unnoticed by someone reading a CAT scan, whereas they may have noticed it more readily if they had been looking at an MRI.
Also, some people are more adept at reading images. Now that they know where the tumor is located, ask your doctor to take another look at the scans taken in 2007 and 2004 to see if they show the tumor and it was merely overlooked before. This is not merely an exercise in curiosity or a gauge of past (in-)competence. Only by looking at a series of scans over time can one gauge the AN's growth trajectory. Has it always been 1.6 cm, all the way back to 2004? Or has it undergone a huge growth spurt in the last few years? Knowing this could have an impact on how often followup scans should be taken or, if you haven't been treated yet, determining if treatment is urgently needed or a watch-and-wait approach is still tenable.
Finally, the quality of past images may have had an impact on the tumor's late discovery. Scanning technology continues to improve. And some facilities offer better (the "latest and greatest") imaging machines than others.
To wit, I have a small hypoglossal tumor (located at the base of the brain) that went unnoticed for at least a couple years. Initial MRI scans revealed the tumor's presence, but radiologists didn't notice it, in part, because the image was fuzzy. A couple years later, I went to Stanford for treatment for my AN. A CT scan was taken to plan my treatment. Once again, the hypoglossal tumor was not noticed, because it was so small and because a CT scan is, once again, hard for the eye to interpret. Five months after receiving CK, I had my first followup MRI series taken at Stanford. (My previous MRIs were all taken at a different facility, not Stanford's.) A radiologist at Stanford noticed my hypoglossal tumor while looking at my first MRI series taken at Stanford. This prompted my Stanford doctors to look at my past MRIs that had been taken elsewhere. I also took a look at all my MRIs. The earliest MRIs show the hypoglossal tumor, but it is a fuzzy image. The one taken at Stanford show a much sharper and clearly defined image of the tumor.
Equipment, a trained eye and the type of scan used -- they all contribute to whether a tumor is noticed early on or not.
Best wishes,
TW
