Suspected or newly diagnosed lymphoma

Lugano classification 2014

For the FDG-avid histologies, PET-CT is the staging study and CT is the fallback. The vetting decisions are getting the sequence right relative to biopsy and treatment, and not accepting a request that expects imaging to make a diagnosis imaging cannot make.

Lymphadenopathy, organomegaly or systemic symptoms with lymphoma suspected, or a tissue diagnosis of lymphoma already made and staging required before treatment.

Referenced decision support — confirm against your local protocol.

Decision support, not a directive. Protocols and timings shown are typical published ones — your local protocol takes precedence, and the vetting radiologist decides.

The request in front of you

Everything is optional. Leave a field alone and the answer assumes nothing — the verdict updates as you go.

Study requested

What the referrer actually asked for. It is evidence of intent, not a constraint on the right answer.

Contrast as written

What the request form says, not what it should say.

Age

Pick a band, or type an exact age if it matters.

years

Pregnancy status

Renal risk factors

The question a vetter can actually answer from the request. An explicit “none known” is a real answer, and it removes checks rather than deferring them.

Previous contrast reaction

The pathway — tap anything already done

Marking a study complete moves the answer on. A patient arrives partway through a pathway far more often than at the start of one.

Accept as requested

FDG PET-CT — skull base to mid-thigh

FDG PET-CT

What we'd amend, and why

FDG uptake reflects the glycolytic activity of lymphoma cells rather than nodal size, so PET-CT upstages normal-sized involved nodes and detects marrow and splenic disease that CT cannot see. It sets the baseline against which the five-point scale is later applied, which is why it belongs before treatment rather than after the first cycle. Fasting and glucose control are part of the study, not preparation trivia: hyperglycaemia competes with the tracer and can render the scan uninterpretable.

Nothing needs resolving before this goes ahead. Routine checks below are owned downstream.

How was this decided?

pathwaystandard — Adults — FDG-avid lymphoma pathway
rulerule-pregnancy-ionising — Pregnancy status before an ionising exposure; checked by Radiographer at the scanner
rulerule-fasting-prep — Patient preparation: fasting, enteric contrast and lactation advice; checked by Scheduling team

Decision support only. Local protocol takes precedence.

Handled at the scanner(2)nothing for you to do

Settled and owned downstream. Each returns to a radiologist only on the stated trigger.

Pregnancy status before an ionising exposure
Make the pregnancy enquiry immediately before the exposure and record the answer. In the UK this is a statutory operator duty discharged at the time of exposure under the employer’s written procedures required by IR(ME)R 2017 — it is not something the vetting radiologist can perform or pre-empt, and a request is complete without it.
Radiographer at the scannerAt the scanner
Flags back if: The patient states that she is, or may be, pregnant AND the uterus is in or near the primary beam. The exposure is then paused for re-justification by the IR(ME)R practitioner before it proceeds.
Patient preparation: fasting, enteric contrast and lactation advice
Confirm the correct preparation was issued and followed. Three separate things are commonly conflated and should not be: (1) routine intravenous iodinated or gadolinium contrast requires NO fast — the ACR Manual states fasting is not required before routine intravascular contrast administration; (2) oral or rectal contrast protocols have their own timing which is a protocol requirement, not a fast; (3) planned sedation or anaesthesia does require fasting, on anaesthetic rather than contrast grounds.
Scheduling teamBefore the scan
Flags back if: The patient has not taken the oral or rectal preparation on which the protocol depends, or is incorrectly fasted or unfasted for a planned sedation or anaesthetic.

Pathways

Big forks are separate pathways; the first whose conditions match is the one used.

Adults — FDG-avid lymphoma pathway

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	FDG PET-CT FDG PET-CT — skull base to mid-thigh usually appropriate	FDG uptake reflects the glycolytic activity of lymphoma cells rather than nodal size, so PET-CT upstages normal-sized involved nodes and detects marrow and splenic disease that CT cannot see. It sets the baseline against which the five-point scale is later applied, which is why it belongs before treatment rather than after the first cycle. Fasting and glucose control are part of the study, not preparation trivia: hyperglycaemia competes with the tracer and can render the scan uninterpretable.
Reasonable alternative	CT Abdomen and Pelvis CT Abdomen and Pelvis — Portal Venous Phase	Contrast-enhanced CT stays the staging study for histologies with unreliable FDG avidity, and is the practical answer where PET access would delay treatment in aggressive disease. It also answers the mechanical questions PET cannot — ureteric or biliary compression, vascular encasement, impending obstruction — which are what decide whether treatment starts today.
Reasonable alternative	CT Chest CT Chest — Contrast-Enhanced (Venous Phase)	Where CT is being used for staging, the thorax is included in the same venous acquisition; bulky mediastinal disease is a prognostic variable in Hodgkin lymphoma and is measured on CT rather than estimated from PET.

Pitfalls

Requesting PET-CT to answer whether a lymphadenopathy is lymphoma. Uptake is not histology; infection, sarcoidosis and reactive nodes are all avid.
Doing the staging PET after the first cycle of chemotherapy, which destroys the baseline the response criteria depend on.
Steroids started for symptom control before staging imaging — common, understandable, and a documented cause of an uninformative scan.
Assuming a negative PET excludes disease in an indolent histology; the FDG-poor lymphomas need CT.
Brown fat uptake in a young thin patient in a cold scanner room, misread as supraclavicular nodal disease.
Booking a staging PET for a patient with airway compromise from a bulky mediastinal mass, or with back pain and new neurology. Those are an urgent CT chest and a same-day whole-spine MRI respectively, and neither of them is a staging question.
Scanning a young patient with Hodgkin lymphoma repeatedly out of completeness. This population is cured and then lives for decades, so surveillance imaging beyond what the protocol requires is cumulative dose in exactly the group least able to afford it.

Priors — what to pull first

Look for older imaging showing the same nodes. Long-standing stable lymphadenopathy shifts the differential considerably.
Where treatment has already started, record it — steroids given before a staging PET can substantially reduce uptake and produce a falsely low burden.

What makes a good request

Imaging does not diagnose lymphoma. Tissue does. Where no biopsy has been taken, the useful imaging question is which node or site to sample and whether there is a more accessible one.
The Lugano classification incorporated FDG PET-CT into standard staging for FDG-avid lymphomas and made routine bone marrow biopsy unnecessary for Hodgkin lymphoma and most diffuse large B-cell lymphoma.
Indolent histologies — particularly marginal zone lymphoma — are variably FDG-avid, and contrast-enhanced CT remains the staging study for those.
Baseline PET-CT before treatment is what makes the interim and end-of-treatment five-point scale interpretable. A treatment started without a baseline leaves response assessment without a comparator.
Two presentations override this sequence entirely and neither waits for a PET slot. A bulky mediastinal mass with stridor, orthopnoea or superior vena cava obstruction needs an urgent contrast-enhanced CT chest now, scanned in a position the patient can actually tolerate and with the anaesthetic and haematology teams aware, because airway collapse on induction is the described catastrophe here. And back pain with any neurological symptom or sign needs same-day whole-spine MRI: lymphoma causes cord compression through epidural extension from a paravertebral mass without destroying bone at all, so a staging PET neither excludes it nor localises it, and dexamethasone and specialist referral are started while the scan is arranged.
Aggressive histology is itself a tempo. Where PET access would delay the start of treatment in Burkitt or high-grade B-cell lymphoma, contrast-enhanced CT now is the right answer and the PET is not worth waiting for.

Scoring this once it is done

The classification and risk tools this question ends in.

Deauville 5-Point Scale with Lugano Response RECIST 1.1 Tumor Response PERCIST 1.0 PET Response

How these studies are acquired

Contrast, phases and timing for every study on the pathways above.

FDG PET-CT — skull base to mid-thigh CT Abdomen and Pelvis — Portal Venous Phase CT Chest — Contrast-Enhanced (Venous Phase)

Confirm locally

FDG PET-CT — skull base to mid-thigh: timings are typical — confirm against local protocol.
Timings, contrast volumes and rates above are typical published values. Your department's protocol, scanner and patient population decide the actual numbers.
Safety thresholds and premedication policy follow local policy where it differs from the cited guidance.

References

Implemented from the cited published sources. Educational and workflow support only; confirm against current guidelines and local policy before clinical use.