At ECR 2026, the session “Rectal cancer staging made simple: TNM classification for radiologists” showed that rectal cancer imaging is only useful when it goes beyond labels and supports treatment decisions. Ioana Andreea Gheonea set out the principles of TNM staging in rectal cancer and explained why MRI adds essential information that classical staging alone cannot provide. Ferdinand Bauer then translated those principles into daily practice, focusing on image quality, angulation, surgical anatomy and the reporting details that can change management.
TNM Plus: Why MRI Changes the Meaning of Staging
Ioana Andreea Gheonea began by stressing that “TNM is not enough in rectal cancer” and that “rectal cancer needs MRI.” Her core message was that tumour depth, nodal status and distant metastasis remain necessary, but they do not fully capture what clinicians need in order to plan therapy. MRI adds two decisive markers: mesorectal fascia and extramural vascular invasion. As she put it, “we do not treat TNM alone. We treat margins and tumour biology.”
She explained that this becomes especially important in T3 disease. Rather than treating T3 as a single block, she showed that its subclasses have different implications. T3a and T3b represent superficial invasion and may still allow primary surgery, whereas T3c and T3d indicate deeper invasion and are more likely to lead to neoadjuvant treatment. In other words, the same broad T category can contain very different prognostic and therapeutic realities.
Mesorectal fascia, she said, is “the key structure for treatment.” Radiologists must report the shortest distance from tumour to fascia and identify when that distance is less than 1 mm, because this marks a high-risk tumour. “Without this,” she warned, “the report, it’s not clinically useful.” She made the same point about EMVI, describing it as “not a local finding” but “a systemic warning sign.” Her summary was blunt: “If you see EMVI, just think liver metastasis.”
Reporting What Matters: Nodes, Deposits and Clinical Usefulness
Gheonea then turned to nodal staging and the frequent traps it presents. Her rule was to “detect, localize and characterize.” Diffusion-weighted imaging can help detect nodes, but localisation relies on high-resolution T2 imaging, and final judgement depends mainly on morphology. Irregular borders, round shape and heterogeneous signal are suspicious, while size alone is secondary. That is why, in her words, “morphology is more important over size” and “small nodes are still a problem.”
She also highlighted tumour deposits, which should not be confused with lymph nodes. These are separate clusters of cancer cells in mesorectal fat or fascia, distinct from the primary tumour, and they carry independent prognostic value. Because of their association with recurrence, metastasis and poor survival, they should be reported separately rather than absorbed into a vague nodal description.
Another practical distinction concerned the roles of MRI and CT. MRI is for local staging, while CT remains the tool for systemic staging and metastatic classification. Gheonea argued that structured templates help radiologists keep these priorities in view. Used consistently, they are not merely a format but a way of learning how rectal cancer should be assessed. Once the logic is understood and image quality is high, staging becomes clearer and more clinically relevant.
From Image Acquisition to Surgical Strategy
Ferdinand Bauer opened by moving “from theory to practice” and by insisting that many errors begin before interpretation. “Bad diagnosis almost starts with poor patient preparation,” he said, adding that “high quality imaging always start with good patient preparation.” His talk made clear that correct preparation, standardised protocol and proper angulation are not technical niceties but the basis of reliable staging.
He emphasised that MRI is “for staging, not for diagnosis” and repeatedly returned to the mesorectal fascia as the decisive structure for the surgeon. It defines the circumferential resection margin and therefore whether surgery can proceed safely. If the tumour is well clear of the fascia, a clear resection may be feasible. If the margin is threatened or involved, surgery alone is not enough. Bauer condensed this into one direct line: “The CRM determines the therapeutic approach.”
Correct angulation was another major theme. He showed that slices must be planned perpendicular to the tumour axis, not simply to the body axis. Otherwise, MRI can falsely suggest invasion into adjacent structures and lead to overstaging. He also urged young radiologists to understand the surgical and pathological context behind the images. Watching total mesorectal excision, handling specimens and seeing how pathology sections are made all change the way MRI is read. “Only then you understand why one millimeter matters,” he said, and “at the end of the day, you will look at MRI images with completely different eyes.”
In his final teaching points, Bauer addressed lateral lymph nodes and advanced imaging. Lateral nodes outside the standard resection field may remain in place after surgery and therefore matter in a different way from small intramesorectal nodes. He also showed how functional imaging can reveal micrometastatic differences even between nodes of identical size. “The same size not mean the same biology,” he said, before reducing the concept to a memorable formula: “Black means healthy, white means micrometastasis.”
Conclusion
The session made rectal cancer staging simpler by showing which details truly matter. Gheonea demonstrated that MRI expands TNM into a clinically useful framework centred on margins, biological risk and treatment planning. Bauer showed that even the best framework fails without proper preparation, correct angulation and a clear understanding of surgery and pathology. Together, the talks argued for a more disciplined kind of radiology: one that does not just assign stage, but helps determine what happens next.
Source & Image Credit: ECR 2026
