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The WHO has long upheld health equity as a guiding principle, emphasising that every individual deserves the highest attainable standard of health regardless of geography or income.1 2 Yet this principle is not fully realised in its most influential product in oncology: the WHO Classification of Tumours, or the ‘Blue Books’. Over time, the WHO tumour classification has shifted towards a more granular, genetically driven framework where H&E microscopy is no longer sufficient to render a complete diagnosis. While this evolution reflects legitimate scientific progress, it risks deepening health disparities for most of the world’s population, which lacks the tools necessary to implement modern diagnostic approaches. The recent iterations of the WHO tumour classification, with their complexity and reliance on molecular criteria, are an unintended consequence of well-meaning efforts. They are designed to maintain a state-of-the-art, cutting-edge standard, but these classifications have instead produced a system that is resource intensive and difficult to operationalise. It is time to reframe WHO’s responsibility: the organisation has a moral mandate to lead structural change, not merely codify science. The classification can strike a balance between aspirational advances and pragmatic equity, serving as a bridge rather than a barrier.Genetic subtyping has obvious appeal, as it enhances diagnostic accuracy, refines prognostic stratification and opens the door to targeted therapies. However, this ideal is unattainable in most low-income and middle-income countries (LMICs). Many pathology laboratories in these places lack access to next-generation sequencing and methylation profiling technologies. In one study of LMICs, local availability of molecular diagnostic techniques for central nervous system tumours was markedly limited: only 29% had access to fluorescence in situ hybridisation, 11% Sanger sequencing, 9% next-generation sequencing and 4% DNA methylation profiling.3 A recent survey examining the feasibility of applying essential diagnostic criteria from the fifth edition of the WHO Classification of Female Genital Tumours revealed a similar discordance.4 Access to recommended immunohistochemical stains (IHC) varied drastically by income level: from 96% in high-income countries to only 13% in low-income countries. Notably, some essential biomarkers were frequently unavailable even in high-income countries, underscoring systemic diagnostic gaps. This situation is becoming untenable for disciplines that are heavily reliant on sophisticated molecular diagnostics, such as neuropathology, haematopathology and bone and soft-tissue pathology. While high-income countries quickly implement the latest WHO classification, pathologists in LMICs are often left to label tumours as ‘not otherwise specified (NOS)’.5 This two-tiered diagnosis system—precise in the Global North, ambiguous in the Global South—undermines WHO’s admirable desire to offer a global standard.Moreover, even when LMICs adopt molecular testing, their clinical value is often limited. Some advances in molecular diagnostics—BCR::ABL translocation, for instance—have transformed cancer care. Unfortunately, such breakthroughs remain an exception. A case in point is the group of round cell sarcomas with EWSR1::non-ETS fusions recognised by the WHO. These tumours require molecular confirmation for diagnosis yet have no therapeutic implications and offer limited clinical value, underscoring how some molecular entities function more as academic distinctions than practical tools. (In the interest of disclosure, one of the authors (VD) helped identify a subset of these sarcomas.6) We must also consider the harms that may accrue. Unnecessary testing can burden laboratories and patients with hundreds or thousands of dollars in expenses while simultaneously introducing diagnostic delays.7 In high-income countries, direct patient payment for IHC tests occurs in just 3% of cases. However, this burden rises substantially to 88% in low-income countries.4Oncologists and pathologists from LMICs have highlighted this disconnect.8 They have noted that experts from North America and Europe dominate the WHO classification process (by our recent count, only 4 out of 20 WHO Standing Editorial Committee members are from the Global South). It is no surprise that guidelines often assume infrastructure that does not exist in much of the world. Some efforts have been made to adapt the WHO classification for use in resource-limited settings.9 The Indian Society of Neuro-Oncology, for instance, published modified guidelines for diagnosing gliomas using only essential IHC, sidestepping molecular tests.10 The WHO has also endorsed using NOS categories as flexible alternatives.5 But such workarounds are unsatisfying and incomplete. Diagnosing a tumour as NOS implicitly signals inferiority and contributes to clinical uncertainty, especially in regions already grappling with inadequate cancer care.11A review of the composition of expert panels for the sixth edition WHO Tumour Classification for Breast, Female Genital, Digestive System, and Soft Tissue and Bone Tumours suggests that this problem has not yet been resolved: roughly 5% of panel members are from LMICs while an overwhelming 95% represent high-income countries.12 This imbalance contrasts sharply with global demographics, where 84% of the world’s population resides in LMICs. Global pathology workforce distribution is also highly uneven, with pronounced regional and income-level disparities. High-income countries have, on average, a far greater density of pathologists (several per 100 000 people) than most low-income and many lower-middle countries (sometimes fewer than 1 pathologist per 100 000). The implication is clear: WHO classifications are predominantly authored by pathologists from affluent settings and tailored primarily for high-resource environments. Consequently, pathologists from LMICs, who deliver care to the majority of the world’s population, remain marginalised and their diagnostic realities inadequately addressed.What would an equitable WHO classification look like in practice? First, the system should adopt a dual-tier framework: a core diagnosis rooted in morphology and basic IHC that can be included in the WHO Essential Diagnostics List. This would be supplemented by molecular refinements placed in appendices. This ensures that all patients, regardless of their geographical location, receive a diagnosis grounded in tools available worldwide, while still leaving room for advanced science in high-resource settings.Second, the WHO could commit to improving global representation on its editorial board. Currently, LMIC contributors are often placed in a separate ‘advisory’ panel—consulted but not empowered to shape the core text. One tactic to improve global representation that was used with the Intergovernmental Panel on Climate Change was to pair each high-income country lead with a co-lead from an LMIC.Third, resources should follow rhetoric. WHO should not only write books but also invest directly in LMIC laboratories and workforce development programmes specific to tumour classifications. This might include fellowships, pilot collaborations with regional centers and funding for essential diagnostic capacity. Investing in capacity-building and mentorship helps assure that the next generation of LMIC pathologists can assume leadership not by exception but by design.Fourth, the field must broaden the definition of ‘expertise’, so that managing thousands of cases in resource-constrained hospitals counts as much as publishing in elite journals. It also means subjecting each new Blue Book to rigorous peer consultation from national societies worldwide, to ensure feasibility and use in real-life situations.Finally, accountability must be embedded into the process. Every Blue Book could be accompanied by an equity impact statement, reporting transparently on geographic representation, diagnostic feasibility surveys and real-world implementation.Our proposal for a morphology-driven and IHC-driven core with molecular refinements in appendices can be operationalised as follows:Criteria for appendix placement: sophisticated or resource-intensive tests (eg, next-generation sequencing, methylation profiling) should be placed in appendices unless they meet clear thresholds of (1) global feasibility, (2) therapeutic impact and (3) affordability.Scaling and flexibility: appendices should be designed as ‘living documents’, updated digitally as new technologies become more widely accessible. In this way, innovations can be rapidly incorporated without forcing premature adoption in settings not yet equipped to do so.Alignment with investments: WHO should keep the Blue Books in step with changes in LMIC capacity. As laboratory infrastructure and workforce training expand through targeted programmes, classification criteria can be progressively updated to incorporate these advances.Human capacity and quality: any restructuring must explicitly address human resources. This includes strengthening workforce pipelines in LMICs, ensuring training in essential diagnostics and providing support for sustainable quality assurance. Without parallel investment in people as well as technology, even the most carefully tiered classification will fall short.None of the changes suggested in this editorial should be seen as charity—we are advocating for justice and pragmatism. Health professionals are more likely to adopt guidelines when they see themselves as part of the process of their creation; patients are more likely to benefit when classifications reflect the realities of their health systems; and the WHO itself is more likely to preserve its legitimacy when its tumor classifications reflect the diversity of the world it seeks to serve.Equity in cancer diagnosis is not just a technical challenge but a moral imperative. Cancer is not merely a disease of the affluent; it is a leading cause of death worldwide, and its burden is rapidly increasing in LMICs.13 Projections estimate that annual new cancer cases will rise from 14.1 million in 2012 to 21.6 million by 2030, with LMICs bearing the greatest burden. Now is the ideal moment to introduce these equitable changes, as the sixth edition of the WHO Classification of Tumours is in process.14 By embracing representation, aligning diagnostic criteria with accessible tools and ensuring that its books evolve in step with laboratory capacity, the WHO can reaffirm its important role as a global standard-setting body. Pathologists can ensure that a woman with breast cancer in Nairobi or Dhaka has access to the same diagnostic accuracy as a patient in Boston or Berlin, not necessarily through identical technologies but through a framework that values practicality as much as precision. Only then can the WHO Classification of Tumours become what it was intended to be: a tool for all the world’s patients, not just a privileged few.