Whole-body MRI, full-body CT and multi-cancer blood tests are good at finding things and were never designed to say what they are. Which second test settles a chest finding depends entirely on where in the chest it sits — and getting that wrong has led to a great many unnecessary operations. Dr Lawrence Okiror, Consultant Thoracic and Robotic Surgeon (GMC 6150382), reviews the report and the images themselves, explains what the finding is and is not, and sets out what — if anything — needs doing. Appointments at London Bridge Hospital and The Lister Hospital Chelsea within 2–3 days, including video consultations. Self-referrals welcome.
Last reviewed: August 2026 · Dr Lawrence Okiror FRCS(CTh) FRCSEd(CTh) · GMC 6150382
These scans survey the whole body rather than answer a question about one organ. The finding is usually real. What it means almost always needs a second, targeted test — and which one depends on where in the chest it sits.
In the front of the chest, CT makes harmless cysts look solid. In the ribs, MRI makes harmless lesions look aggressive. In the lungs, MRI misses small nodules altogether. Knowing which way the error runs is most of the interpretation.
The usual outcome of sending me one of these reports is reassurance with a defined interval, or a single targeted scan that closes the question. Surgery is arranged only for the minority who need it.
Because of what was there before anyone looked. When a scan is arranged for a symptom, a risk factor or an abnormal result, there is already a reason to think something might be found, and everything on the images is read against that reason. A scan bought as a health check has no such reason behind it. You were well. Nothing prompted it. The likelihood of serious disease was low before the machine was switched on, and it is still low afterwards.
This is not an argument that the finding does not matter. It is an argument about how it should be read. The same appearance carries different weight depending on what preceded it, and a report written without that context can sound far more definite than the evidence allows. Words like likely represents and cannot be excluded are doing a great deal of work.
What follows is what these scans and tests actually do well, what they do badly, and what the sensible next step is for each part of the chest. For what CT, MRI and PET each contribute more generally, and what the standard phrases in a radiology report mean, the chest imaging page covers that ground.
Every scan sold as a health check is better at finding things than at saying what they are, and which second test settles the question depends on where in the chest the finding sits. The five parts of the chest behave differently, and so do the mistakes.
| Where in the chest | Which scan settles it |
|---|---|
| Front of the chest and thymus | CT finds it; targeted MRI settles whether it is fluid or solid |
| Middle and back of the mediastinum | CT finds it; MRI settles whether it is a harmless cyst |
| Ribs, breastbone and spine | CT both finds and settles it; MRI can look more alarming than the lesion is |
| Lungs | CT both finds and settles it; MRI misses small nodules |
| Chest wall and lung lining | CT finds it; MRI or ultrasound characterises it |
Less than the word suggests, and for reasons that are specific rather than reassuring noises. The thymus sits directly behind the breastbone. It is a normal organ, it is often still clearly visible in younger adults, and it enlarges again after illness, physical stress, steroid treatment or chemotherapy. It is, in other words, frequently seen — and on a scan looking for cancer, frequently remarked upon.
A triangular or arrowhead-shaped structure at the front of the chest, with a smooth outline, two symmetrical lobes and no discrete lump inside it, is the appearance of thymus. A thymoma is a discrete rounded or lobulated mass — a lump that stands apart from the tissue around it. Age matters too: normal and enlarged thymus is common in younger adults and becomes progressively less so with age.
Shape alone does not settle it, which is precisely why the additional MRI sequences exist. There is a published case of a thymoma that looked smooth and symmetrical on CT, was reported as an enlarged normal thymus, and was correctly identified only when the extra sequences were run.
The sequence that answers the question takes a few extra minutes. It works by detecting microscopic fat inside the tissue — normal and enlarged thymus contains it, a thymoma does not, and the signal drops accordingly. In published series this separates the two almost perfectly. It is not part of a whole-body screening protocol, so if your scan has raised the question, the test that answers it has usually not yet been done.
Alongside that sits the cyst problem. A thymic cyst is a benign fluid-filled sac that needs no treatment, but where it contains protein it carries the same density on CT as a solid tumour, and small ones sitting close to the aorta can appear to take up contrast when they have not. That is how unnecessary thymus operations happen, and it is avoidable with one targeted scan.
This is the situation people find hardest, and it deserves an honest answer rather than a confident one. A blood test has reported a signal. A scan has been arranged. Nothing has been found, or something unrelated has. And the question that remains — what now — has no agreed answer anywhere in medicine.
Two things are worth knowing before anyone offers you a plan. In people without symptoms, a positive result on these tests is more often wrong than right — not because the tests are poorly made, but because serious disease is uncommon in a well population, and even a very accurate test produces more false alarms than true ones when it is applied to people who are unlikely to be ill.
In the largest published experience of a multi-cancer blood test used this way, resolving a positive result took around two months where a cancer was eventually found — and around five months where none was. A quarter of people waited eight months or longer. A later and larger study reported considerably shorter times, so this is improving, but the pattern holds: the false alarms take longest to close.
Published work in this field states plainly that where the first round of investigation comes back negative or equivocal, it is not known how closely such people should then be followed. Anyone who gives you a confident surveillance protocol is going beyond the evidence.
What I can do is take responsibility for the chest half. That means reviewing the imaging properly rather than reading the report, deciding whether anything in the chest genuinely needs characterising, and giving you a defined interval and a defined end point rather than an open-ended arrangement to keep scanning. Where the answer is that nothing in the chest requires anything, I will say that.
One practical note. The test most people have heard of is not necessarily the one they have had. Galleri, the multi-cancer blood test most widely reported and the subject of a large NHS trial that reported in 2026, was for several years available in the UK only within that trial. It carries a UKCA mark and began to be offered privately here during 2026 through a small number of providers, though it remains unavailable on the NHS. UK clinics also sell several other tests, and what a positive result means differs between them. Bring the actual report rather than the brand name.
Most people who send me one of these reports need no operation. The usual outcome is an explanation, reassurance with a defined interval, or one targeted scan that closes the question. That is worth saying at the outset, because a page like this is easily mistaken for an invitation to be operated on.
The consultation is a review of the images themselves rather than the report. Reports are written to be defensible and frequently sound more equivocal than the pictures are. Looking at the actual images, with you, and explaining what is there, is the part that changes anything — and it is what most people have not yet had.
If further imaging is needed, it is one targeted study aimed at the specific question, not another survey. Where you live at a distance it can usually be arranged locally and reviewed at a follow-up. Only the minority who need an operation come to London, to London Bridge Hospital or The Lister Hospital Chelsea.
I do not deal with the findings outside the chest, and these scans produce plenty of them — liver, kidneys, adrenal glands, prostate, spine, brain. Taking those on would not serve you. I will tell you which of them look as though they warrant a specialist opinion and which are the common harmless ones, and say so clearly rather than leaving you to work it out.
And I do not offer a view on whether you should have had the test. People choose these deliberately, usually after reading a good deal, and being lectured about it afterwards helps nobody. My job starts at the point the result exists.
Appointments at London Bridge Hospital and The Lister Hospital Chelsea are usually available within 2–3 days, including video consultations, and patients are seen from across the UK and internationally. Where a case is genuinely uncertain it is discussed at the chest multidisciplinary team meeting before any surgical decision. If you have already been given an opinion you are unsure about, a second opinion is a reasonable thing to want.
The statements on this page are deliberately written without technical vocabulary. For anyone who wants the underlying numbers, they are set out here in full.
Questions people ask after a whole-body scan, a full-body CT or a cancer blood test has raised something in the chest.
Book a Consultation →Or call Jo Mitchelson:
020 7952 2882
Self-referrals welcome. Appointments at London Bridge Hospital and The Lister Hospital Chelsea within 2–3 days, including video consultations, with outpatient clinics at Canary Wharf and the City of London. Send the report, the images and any blood test result. Most people who do need no operation.
Jo Mitchelson, PA · 020 7952 2882 · pa@lungsurgeon.co.uk
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