Measurement deviations of lung nodule

Yea remember it’s a picture until they get their hands on it - so to speak. My tumor was measured on CT
at 14mm. But a month later when they took it out the pathologist called it 2cm - but then scored it less than 2. So other than crossing a somewhat arbitrary threshold of severity, I can’t see it really matters.

Measurements can and do change over time. @pb50 is right to point out that a CT scan is a picture and a fuzzy picture at that. I wouldn't even call it a margin of error but rather a degree of uncertainty. A PET scan measures something else and can give a different estimated size. Oncologists are trained to know what is concerning and what is not.

Is your doctor concerned, or are you curious?

I have several nodules being watched, but for multifocal lung cancer. This type of lung cancer acts differently than other cancers in that the nodules are considered primary cancers (not metastasis, although some could be). It is an indolent cancer and tends to stay in the lung. Anyway, the nodules can change over time. They mature from "ground glass" on the CT scan to semi-solid to solid so the measurements change depending on what they are referring to. And I have two removed nodules and the measurements were different from what was on the CT scan.
I am followed at Mayo so they know why I am there and set the scan machine to pick up smaller nodules. I had to have two CT scans in the ER locally in the last two years and their results were a lot different in the description of my nodules. Not their specialty.

I don't know if there is a "margin of error" depending on the machine. At Mayo they have not tried to keep me on the same machine. With bone density tests there is an issue and one should stay on same machine

From what I've observed with mine 2mm is not considered substantial enough but I don't know the margin that is. Measurements can vary depending on the exact image number they use, if it was done on a different machine, if it was read by a different radiologist, or how far the lung was expanded when the patient held their breath. The study I'm sharing here is old but it highlights how subjective interpretations can be.
https://cancergrace.org/post/did-my-cancer-grow-10-minutes-limitations-ct-scanning

I think your point is valid that imaging something that small and different scanners and different radiologists could produce small variances . The article is informative.
As you mentioned the article is old and am wondering how old the CT was when they did this test. Since the first CTs were developed, the medical equipment manufacturers have continually improved their CTs to maximize image quality while minimizing radiation dose. CTs were replaced quite often just because of vast improvement in scanning capabilities. Point being, I would like to see the test repeated today. Also, the scanner settings can vary widely based on physician need. body part, patient age, etc. There is a lot of on-line information and can get quite technical. This is a short YouTube basic explanation of images. Hope this helps

I’m going to guess you meant 2cm not 2mm.. the latter would be very very small