A thymoma diagnosis raises specific questions that few non-specialist teams encounter often. The histological subtype matters. The Masaoka-Koga stage matters. The decision between immediate surgery, neoadjuvant chemotherapy, and multimodality treatment depends on a careful reading of imaging and pathology against the published recommendations of the International Thymic Malignancies Interest Group (ITMIG). Many patients are referred for a second opinion before committing to treatment — at this practice, that is a routine part of the work, not an exception. Mr Okiror offers private thymoma surgery and second-opinion consultations at London Bridge Hospital and The Lister Hospital Chelsea.
Last reviewed: July 2026 · Mr Lawrence Okiror FRCS(CTh) FRCSEd(CTh) · GMC 6150382
Thymic epithelial tumours are not a single disease. Two independent variables determine almost every operative and oncological decision: the WHO histological subtype (A, AB, B1, B2, B3, and thymic carcinoma) and the anatomical stage. The 2021 WHO classification (5th edition) refines the diagnostic criteria for these categories while retaining the established nomenclature; type B3 and thymic carcinoma carry the highest recurrence risk and the strongest case for multimodality treatment. The second axis is now anchored by the ninth edition TNM classification (TNM-9), which took effect in January 2025 as the global standard. Most patients arrive holding a Masaoka-Koga stage instead — that system is not wrong, it is superseded, and it maps directly onto TNM-9.
The intersection of these two axes governs the surgical question. An encapsulated type A or AB thymoma at Masaoka-Koga stage I is a different operation, with a different sequencing of investigations and a different post-operative pathway, than a type B3 thymoma with capsular invasion at stage III. A solitary type B2 at stage II requires a different post-operative surveillance schedule than the same subtype at stage IIB. Thymic carcinoma at any stage is treated as a distinct clinical entity, with surgery the cornerstone but multimodality treatment the rule, not the exception.
This page is structured around that matrix. The sections that follow — on histological subtype, staging, surgical approach, sequencing of multimodality treatment, and assessment for paraneoplastic disease (most commonly myasthenia gravis, present in 30–50% of thymoma patients) — all return to the same two questions: what subtype, what stage. The decision is not made by surgical preference. The decision is made by the matrix.
Key takeaways
The thymus is a small gland in the front of the chest, behind the breastbone, that plays a central role in the development of the immune system in early life. In adulthood it becomes largely inactive — but in some adults it gives rise to tumours. These are called thymic epithelial tumours, and they are rare: approximately two cases per million people per year.
Thymomas are not all the same. The World Health Organization classifies them into six types — A, AB, B1, B2, B3, and thymic carcinoma (sometimes called Type C) — reflecting increasing biological aggressiveness. Type A and AB tend to behave indolently. Type B2 and B3 are higher-grade. Thymic carcinoma behaves more like other aggressive cancers and has a fundamentally different treatment pathway. The 2021 WHO 5th edition classification refines the diagnostic criteria for each subtype while retaining the established nomenclature.
Histological subtype, together with the tumour stage, determines the treatment plan. Both must be confirmed by an experienced thoracic pathologist before any treatment is recommended. If either has not been clearly established at diagnosis, that is the first thing a specialist consultation should resolve.
Mediastinal pleural invasion was removed as a T descriptor in the ninth edition because it is difficult to identify reliably, but it is still recorded as an additional histological descriptor.
Masaoka-Koga was the standard for decades and is still quoted in some guidelines, so many patients arrive holding one. It translates. Stages I and II both correspond to TNM-9 stage I — large database analyses found no outcome difference between them. Most stage III tumours fall into TNM-9 stages II and III, which separates them more usefully for treatment planning. Stages IVA and IVB correspond closely, with TNM-9 adding detail on lymph node involvement. Nothing is lost in the translation; ITMIG now recommends reporting in TNM-9.
A thymoma diagnosis is not a single clinical entity with a single treatment. The right operation — or whether surgery comes first at all — depends on histological subtype, the precise Masaoka-Koga stage, and the assessment of whether complete (R0) resection is achievable. Four broad clinical scenarios cover the majority of patients, and each has a different evidence base and pathway.
Masaoka-Koga Stage I & II
Curative-intent surgery · ITMIG & NCCN recommended pathway
For encapsulated and minimally invasive thymomas, surgery is the primary treatment and offers an excellent chance of cure. Five-year survival is 89–100% for Stage I and 71–97% for Stage II after complete resection. Robotic extended thymectomy — removing the thymus en-bloc with the surrounding mediastinal fat between both phrenic nerves and the innominate vein, per ITMIG technical recommendations — is well-established for these stages.
For Stage II disease with capsular invasion, post-operative radiotherapy may be considered depending on margins, histological subtype, and individual MDT recommendation.
Masaoka-Koga Stage III
Neoadjuvant chemotherapy · surgery · post-operative radiotherapy
For tumours invading the pericardium, lung, or great vessels, immediate surgery may not achieve complete resection. The standard pathway is neoadjuvant cisplatin-based chemotherapy — most commonly CAP (cyclophosphamide, doxorubicin, cisplatin) or PE (cisplatin, etoposide) — followed by surgery if R0 resection becomes feasible, then post-operative radiotherapy.
Some Stage III tumours are directly resectable without neoadjuvant treatment. The decision is made at MDT after detailed review of imaging, considering the tumour's relationship to critical structures and the likelihood of achieving complete resection at first operation.
Masaoka-Koga Stage IVA
Pleural/pericardial spread · specialist surgical capability required
Stage IVA disease — with pleural or pericardial dissemination — was traditionally considered unresectable. International experience now shows that, in selected cases, extended resection within a multimodality regimen can achieve excellent long-term survival. This may include pericardial resection, partial lung resection, vascular reconstruction, or pleurectomy/decortication for diffuse pleural disease.
These cases require a centre with both thoracic surgical experience in advanced thymoma and immediate access to cardiac surgical support for cases where reconstruction of major vascular structures is required.
High-Grade B3 & Thymic Carcinoma
Chemotherapy · radiotherapy · surgery · emerging immunotherapy role
Type B3 thymoma and thymic carcinoma behave more aggressively than lower-grade thymomas. Treatment is almost always multimodality — integrating platinum-based chemotherapy, radiotherapy, and surgery — sequenced according to stage and resectability. Five-year survival for thymic carcinoma is around 30%, considerably lower than for thymoma overall.
The role of checkpoint inhibitor immunotherapy is emerging in this group specifically — covered separately below, with important caveats about autoimmune side effects unique to thymic tumours.
A note on the evidence base
Thymoma is rare. There are no large randomised controlled trials in thymoma surgery comparable to those that exist in lung cancer. International recommendations — from ITMIG, NCCN (v2.2025), and ESMO Clinical Practice Guidelines (Girard et al., Ann Oncol 2015) — are based on registry analyses, prospective cohort studies, and consensus expert opinion. This is acknowledged honestly in those guidelines, and it is one reason why every thymoma patient benefits from review at a centre that sees the full spectrum of disease.
Complete (R0) resection is the strongest predictor of long-term survival in thymoma. The clinical question at every consultation is whether complete resection is achievable now, achievable after neoadjuvant treatment, or unlikely to be achievable at all.
Stage I and II thymomas. Encapsulated or minimally invasive disease. Complete resection achievable robotically with a single operation. The vast majority of these patients will not require chemotherapy. Some Stage II tumours benefit from post-operative radiotherapy depending on margins and histology.
Stage III tumours with major vascular or pericardial invasion where R0 resection is doubtful at first operation. Stage IVA with limited pleural disease. Neoadjuvant chemotherapy — typically three cycles of CAP or PE — can shrink the tumour and increase the likelihood of complete resection at the subsequent operation.
Stage IVB disease with distant metastases or extensive lymph node involvement — treated with systemic therapy. Diffuse pleural disease where pleurectomy/decortication cannot achieve meaningful clearance. Patients whose comorbidities make extended thoracic surgery unsafe. In these cases, an honest conversation about realistic goals matters more than offering an operation.
Node involvement in thymic tumours was under-recognised for years, and the 2026 ITMIG standards now set out what a thymic operation should sample. For stage I thymoma, removal of the adjacent and prevascular mediastinal nodes. For stage II to IV thymoma, a systematic prevascular mediastinal node dissection, with sampling of the deeper stations such as the paratracheal nodes and the aortopulmonary window. For thymic carcinoma and thymic neuroendocrine tumours, systematic sampling of both node groups as a minimum. Nodes are recorded by station using the ITMIG/IASLC node map, not described loosely.
The objection sometimes raised against robotic and keyhole thymectomy is not the size of the incision but the risk of disturbing the tumour on the way out. ITMIG answers it with a specific standard: a minimally invasive approach is appropriate, provided the tissue is not disrupted and the specimen is removed inside a retrieval bag so that nothing is spilled. Any area of concern is marked at the moment it is dissected, both on the specimen and inside the patient, and the specimen is orientated with the pathologist rather than handed over unlabelled. This is how a keyhole operation is held to the same standard as an open one.
At consultation, Mr Okiror reviews CT and PET-CT imaging personally, examines the histopathology report against ITMIG diagnostic criteria, and where relevant requests review by a dedicated thoracic pathologist. Every thymoma patient is discussed at a chest multidisciplinary team meeting before any operation is recommended — including, where useful, virtual consultation with the international ITMIG tumour board.
Every thymoma patient under Mr Okiror's care is discussed at a multidisciplinary team meeting before any treatment is recommended. The team includes thoracic surgery, medical oncology, radiation oncology, thoracic radiology, and histopathology. Where relevant, a respiratory physician and a specialist neurologist for myasthenia gravis are also part of the discussion.
For complex cases — particularly Stage IVA disease, recurrent thymoma, or unusual histology — the MDT may also involve consultation with the ITMIG virtual tumour board, an international forum specifically created so that centres without dedicated thymoma expertise can access specialist opinion. ITMIG explicitly recommends this for complex cases. Mr Okiror's practice routinely uses this resource where it adds value.
Every patient with a thymoma diagnosis is also assessed for myasthenia gravis. Approximately 30–50% of thymoma patients have or develop MG, and NCCN guidelines (v2.2025) recommend clinical evaluation for signs of myasthenia gravis and other paraneoplastic syndromes in every thymic tumour case, with appropriate workup and treatment by a neurologist experienced in myasthenia gravis where present. Where MG is identified, the perioperative pathway changes substantially. See MG thymectomy page →
In selected Stage III and IVA cases where the tumour involves the superior vena cava or other major vascular structures, surgery is performed in collaboration with cardiac surgical colleagues. These cases are uncommon, but they are precisely the operations that distinguish a specialist thymoma centre from a general thoracic practice.
Ten years, and sometimes longer — which surprises most patients, because it is far longer than the surveillance offered after many commoner cancers. The reason is not that thymoma usually comes back. It usually does not. The reason is that thymoma keeps a different clock, and on the uncommon occasions it does return, it can do so a decade after the operation.
A contrast-enhanced chest CT is taken three to six months after the operation, once the changes caused by surgery itself have settled. That scan becomes the baseline everything afterwards is compared against.
For a completely resected stage I thymoma, imaging is annual and continues to ten years. Beyond that, extended-interval MRI is optional; ITMIG is candid that the value of surveillance past ten years is poorly defined.
For stage II to IV thymoma, and for thymic carcinoma and thymic neuroendocrine tumours at any stage, scanning is six-monthly for the first three years, then annual to ten. These are the groups in which recurrence, when it happens, tends to happen earlier.
Imaging runs from above the collarbone down to the middle of the kidneys, so that the whole pleural surface is covered. Thymoma recurs on the pleura more often than anywhere else, and a scan limited to the chest can miss it.
MRI can be substituted for CT to reduce cumulative radiation exposure. This matters particularly for younger patients, who may be scanned annually for a decade or more, and for anyone who cannot tolerate contrast.
PET-CT is not part of routine surveillance. It is used to answer a specific question when one arises — for example, when something on a CT is uncertain and needs characterising.
ITMIG, NCCN and ESMO all arrive at roughly the same answer. NCCN recommends chest CT every six months for two years and then annually to ten years for thymoma, and annual imaging for five years for thymic carcinoma. ESMO suggests follow-up may continue for ten to fifteen years.
None of them can say why ten rather than eight or twelve, and they say so. NCCN states plainly that the duration, frequency and type of imaging used for surveillance have never been tested prospectively. The honest position is that long follow-up is offered to everyone because we cannot yet identify in advance the small number of patients who will need it. That is a reason to keep the appointments, not a reason to worry between them.
Immunotherapy has transformed the treatment of many cancers over the past decade. Patients diagnosed with thymoma understandably want to know whether this applies to them. The answer is genuinely nuanced — and it differs significantly between thymoma and thymic carcinoma.
Thymic tumours frequently express PD-L1 — a target for checkpoint inhibitor drugs such as pembrolizumab and nivolumab. PD-L1 positivity is reported in 23–92% of thymomas and 36–100% of thymic carcinomas. On paper, this should make them excellent candidates for immunotherapy. In practice, the picture is more complicated, because the thymus itself is central to immune tolerance — the mechanism that prevents the immune system from attacking the body's own tissues. Thymoma involves defective immune tolerance. When checkpoint inhibitors release the brakes on the immune system, thymoma patients have significantly higher rates of severe immune-related side effects than any other solid tumour. Myositis, myocarditis, and multisystem autoimmune inflammation are disproportionately common.
For thymoma (Types A through B2), this means checkpoint inhibitors are not routine treatment. They are not part of standard first-line or adjuvant care. They may be considered in carefully selected recurrent or refractory cases at specialist centres, with intensive monitoring for autoimmune side effects.
For Type B3 thymoma and thymic carcinoma, the evidence is more developed. Pembrolizumab monotherapy in pre-treated thymic carcinoma has shown overall response rates of approximately 25% and durable benefit in a subset of patients, with high tumour PD-L1 expression associated with better response (Giaccone et al., Lancet Oncology 2018). The PECATI trial (Remon et al., Lancet Oncology 2025) reported that pembrolizumab combined with lenvatinib achieved a 5-month progression-free survival rate of 88.4% and a median progression-free survival of 14.9 months in pre-treated B3 thymoma and thymic carcinoma — a meaningful result in this difficult disease group, though immune-related toxicity required close monitoring.
Decisions about immunotherapy in any thymic tumour are made jointly with a medical oncologist with thymic-specific experience, after careful review of histology, prior treatment, and the individual risk profile. They are never made unilaterally, and they should never be made without specialist input.
Thymoma is a rare tumour. Many hospitals across the UK see only one or two cases a year. This makes individual surgeon and unit experience an unusually important consideration when choosing where to be treated.
The 2024 SCTS national audit reports that the thoracic surgical unit at Mr Okiror's NHS base performs over 10% of all thymectomies across the United Kingdom and Ireland — the highest single-centre volume of thymic surgery in the country. This is published institutional data from the Society for Cardiothoracic Surgery, not an internal claim. The same operative approach, the same MDT framework, and the same standard of perioperative care apply to private patients seen at London Bridge Hospital and The Lister Hospital Chelsea.
Mr Okiror's personal experience covers the full thymoma spectrum — from robotic thymectomy for early-stage tumours through to multimodality management of Stage III and IVA disease, including cases requiring vascular reconstruction. Patients have included international referrals for second opinion and for surgery. As Clinical Audit Lead for Thoracic Surgery, Mr Okiror is responsible for the submission and verification of the unit data referenced above.
Mr Okiror consults and operates at both London Bridge Hospital and The Lister Hospital Chelsea. Both hold the da Vinci Xi robotic platform and are appropriate settings for robotic thymectomy in Stage I and II disease.
For Stage III and IVA cases — particularly those requiring multimodality treatment, extended resection, or vascular reconstruction — surgery takes place at London Bridge Hospital, where the level of perioperative support and access to cardiac surgical colleagues match the complexity of the operation.
Outpatient consultations are also available at HCA clinics in Canary Wharf and the City of London. International patients who travel specifically for thymoma assessment can be accommodated, and remote review of imaging and histology can be arranged before travel.
Insurance and self-pay: Mr Okiror is recognised by all major UK private medical insurers including AXA, BUPA, WPA, Vitality, Cigna, and Aviva. Self-pay and international patients are equally welcome. Multimodality treatment may involve several components and prolonged care — transparent estimates are provided by Jo Mitchelson before any commitment is made — 020 7952 2882 or pa@lungsurgeon.co.uk.
For a tumour as rare as thymoma, the variation in treatment recommendations between centres can be substantial. Three questions are reasonable before committing to any plan, and any thoughtful surgical team should welcome them.
Both must be clearly established before a treatment plan is finalised. If your team has not given you a specific WHO type (A, AB, B1, B2, B3, or thymic carcinoma) and a specific Masaoka-Koga stage, ask why. Treatment for Type A Stage I differs fundamentally from treatment for B3 Stage III, and neither should be planned without clarity on both.
A general thoracic MDT may see one or two thymomas a year. ITMIG — the international thymic tumours interest group — recommends virtual tumour board consultation for centres without dedicated thymic expertise. Asking whether your case has been reviewed by specialists who see thymoma at volume is a clinically appropriate question.
For Stage III and IVA disease, the sequence — whether neoadjuvant chemotherapy comes first, whether immediate surgery is appropriate, whether radiotherapy is part of the plan — matters greatly for outcomes. Each component should be justified against the imaging findings and the specific WHO subtype, not chosen by default.
A second opinion appointment with Mr Okiror is typically available within 2–3 days. Bring your CT, PET-CT, biopsy report, and any treatment recommendation already received.
If your thymoma comes with myasthenia gravis
Thymomatous MG requires a more complex pathwayAround 30–50% of thymoma patients have myasthenia gravis. The oncological indication for thymectomy is independent of the MG — but the perioperative pathway, the choice of anaesthesia, and the post-operative monitoring all change substantially when MG is present. The dedicated MG thymectomy page covers this in detail.
Common questions from patients and families newly diagnosed with thymoma or thymic carcinoma, and from those seeking a specialist second opinion before committing to a treatment plan.
Book a Consultation →Or call Jo Mitchelson:
020 7952 2882
Appointments within 2–3 days. Self-referrals and international referrals welcome. Surgery at London Bridge Hospital and The Lister Hospital Chelsea.
Jo Mitchelson, PA · 020 7952 2882 · pa@lungsurgeon.co.uk
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Robotic thymectomy for myasthenia gravis — the MGTX evidence, perioperative pathway, and antibody-based patient selection
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