What an 'Indeterminate Lesion' on a Scan Means

This page is for people whose scan report mentions an "indeterminate lesion." It explains what the phrase means, what usually happens next, and practical steps to take.

A lesion is any area of tissue that looks different from what is around it. The word carries no verdict. A bruise, a cyst, a scar and a tumor are all lesions. Indeterminate means that on this scan, the area does not have the classic look of any one thing. So the radiologist will not label it from these images alone.

Put plainly, indeterminate is a statement about the picture, not about you. It says the test reached the edge of what it can show.

Imaging measures density, shape, size, edges, and how tissue takes up contrast (a dye that helps some tissues show up). Harmless and serious things can look alike, especially when small. Indeterminate means the images do not support calling it benign or malignant.

Several ordinary things push a finding into this category:

• The lesion may be small.
• It may sit at the edge of the scanned area.
• Breathing or bowel movement may have blurred it.
• The scan may have been done without contrast, or with contrast timed for a different organ.
• There may be no earlier scan to compare against.

There are usually three paths. Which one is chosen depends on the organ, the size, and your overall risk.

No further action. For some small findings, the team may decide no follow-up is needed. That depends on the organ, size and your risk.

The finding is watched. A repeat scan after a set time answers a question one snapshot cannot: is it changing? Waiting is not doing nothing here. The repeat scan is the test.

The finding is characterized further. A different technique may settle what the first scan could not. That might be MRI instead of CT, a dedicated protocol, an ultrasound, or sometimes a biopsy.

A recommended repeat scan can feel alarming. It often just means the first scan could not settle the question. Ask your team why the timing was chosen. If you notice new symptoms before the scan, call your care team right away.

Indeterminate findings feel different when you are already in treatment. They are also very common in that setting. Earlier surgery, radiation or infection can leave changes that may look like disease on a scan. This is one of the main reasons scans are compared against earlier ones rather than read on their own. Ask your team how this finding fits with your treatment plan.

Note where the word appeared. The Findings section lists everything visible. The Impression carries the radiologist's actual conclusion and recommendation. If a finding is in Findings but not the Impression, ask why.

Check whether a comparison study existed. If the report says no priors available, then part of the uncertainty is simply missing history. Any outside imaging you have had elsewhere may clear it up. Asking for those images to be sent to your team is concretely useful.

Confirm the recommended follow-up is on the calendar. The most common practical harm from an indeterminate finding is not the finding itself. It is a follow-up scan that quietly never gets booked. Ask who is responsible for ordering it, and when you should expect the appointment. Then note the date somewhere you will see it.

• NCI Dictionary - Lesion
• American College of Radiology - Reporting and Data Systems