Thymoma (WHO types A, AB, B1, B2 and B3)
Thymoma is the slower-growing kind of thymic epithelial tumour, an indolent cancer of the thymus gland behind the breastbone that often announces itself through the autoimmune disease myasthenia gravis. Complete surgical removal cures most patients, radiotherapy is added when the tumour has grown through its capsule, and chemotherapy is used to shrink large tumours or control spread in the chest.
Overview
Thymomas are tumours of thymic epithelial cells mixed with non-neoplastic immature T lymphocytes, classified by the WHO into types A, AB, B1, B2 and B3 by the shape of the epithelial cells and the density of lymphocytes, with B3 the most aggressive and A and AB the most indolent. Type A and AB tumours nearly all carry the GTF2I L424H mutation, a finding unique to thymoma, while B thymomas have few recurrent mutations. Because the thymus educates T cells, thymomas are tied to autoimmunity: about a third of patients have myasthenia gravis, others have pure red cell aplasia, hypogammaglobulinaemia (Good syndrome) or other autoimmune conditions, and acetylcholine receptor antibodies are checked before any operation so that myasthenia can be controlled first. Stage, whether by the Masaoka-Koga system or the TNM system introduced in 2017, and completeness of resection matter more than histology for survival.
Surgery is the treatment. Encapsulated tumours are removed whole with the thymus, increasingly by video-assisted or robotic approaches, and the guidelines advise against preoperative biopsy of a resectable encapsulated mass. Postoperative radiotherapy is recommended for stage III disease and for incomplete resection and considered for stage II B2 to B3 tumours, and unresectable or bulky tumours are given induction chemotherapy with cisplatin, doxorubicin and cyclophosphamide (CAP) or a platinum-etoposide doublet before reassessment for surgery. Pleural spread is treated with repeated resection or, in some centres, pleurectomy. For recurrent disease not amenable to local treatment, chemotherapy is repeated, octreotide with prednisone helps octreotide-scan-positive tumours, everolimus produced disease control in a phase 2 trial, and sunitinib and lenvatinib have activity; PD-1 antibodies are used with great caution because thymoma patients develop severe myocarditis, myositis and other immune toxicity far more often than other cancer patients. Thymoma recurs late and slowly, so follow-up runs for at least ten years.
State of the art
- Complete resection cures most thymomas and minimally invasive thymectomy is now routine for small tumours.
- The 2017 TNM system unified staging across the world's thymic registries.
- Immunotherapy is the one modern treatment largely closed to thymoma patients because of autoimmune toxicity.
Red cards
From the labels and guidelines behind the standard of care. Your team's thresholds win.- Emergency services nowBleeding or bruising
Bleeding that will not stop, black or bloody stools, or unexplained bruising when platelets are expected to be low.
- Emergency services nowBowel perforation
Sudden severe abdominal pain, a hard or very tender abdomen, or abdominal pain with vomiting and fever. Boxed warning for gastrointestinal perforation on bevacizumab.
- Emergency services nowFainting or palpitations
Fainting, near-fainting, or an irregular or racing heartbeat; several kinase inhibitors prolong the QT interval and the labels require ECG and electrolyte monitoring.
- Check before combiningSunitinib with Lenvatinib: major interaction
QT: both Sunitinib and Lenvatinib prolong the QT interval (known and known risk).. Avoid other QT-prolonging drugs where possible; check ECG and correct potassium and magnesium before and during treatment.
- Check before combiningFood and drink: Doxorubicin
Cumulative dose: risk rises steeply above 400-550 mg/m² (see the anthracycline calculator).
- Check before combiningFood and drink: Everolimus
Avoid grapefruit. Live vaccines are contraindicated.
See all on the product pages:CarboplatinCisplatinCyclophosphamideDoxorubicinEverolimusLenvatinibPaclitaxel / nab-paclitaxelSunitinib·Printable cards in the navigator
Anatomy and lymph node drainage
- Central airways (squamous, small-cell)
- Periphery (adenocarcinoma)
- Apex (Pancoast)
- Pleura (mesothelioma)
- Thymus (anterior mediastinum)
- Nodes: hilar (N1)
- Nodes: mediastinal (N2)
- Nodes: supraclavicular (N3)
Central tumours arise in the large airways, peripheral ones in the alveoli; both drain to hilar then mediastinal nodes, and the pleural lining is a separate cancer site.
- Central airways (squamous, small-cell)
- Periphery (adenocarcinoma)
- Apex (Pancoast)
- Pleura (mesothelioma)Stage III to IVA thymoma with pleural spread
- Thymus (anterior mediastinum)Type A thymoma (spindle cell, indolent, GTF2I mutant) · Type AB thymoma (mixed, indolent, GTF2I mutant) · Type B1 thymoma (lymphocyte-rich) · Type B2 thymoma · Type B3 thymoma (epithelial-rich, the most aggressive thymoma) · Thymoma with myasthenia gravis or other paraneoplastic autoimmunity · Micronodular thymoma with lymphoid stroma (rare, indolent) · Stage III to IVA thymoma with pleural spread
- hilar (N1)
- mediastinal (N2)
- supraclavicular (N3)
Same organ: Non-small-cell lung cancer, Lung cancer (all types), Small-cell lung cancer, Mesothelioma, Pleural mesothelioma, Thymoma and thymic carcinoma, Childhood lung and airway tumours (pleuropulmonary blastoma, tracheobronchial tumours), Inflammatory myofibroblastic tumour (IMT), EGFR-mutated non-small-cell lung cancer, ALK-positive non-small-cell lung cancer, KRAS G12C-mutant non-small-cell lung cancer, ROS1-positive non-small-cell lung cancer, MET exon 14 and MET-amplified non-small-cell lung cancer, RET fusion-positive non-small-cell lung cancer, BRAF V600E-mutant non-small-cell lung cancer, HER2-mutant non-small-cell lung cancer, NTRK fusion-positive non-small-cell lung cancer, PD-L1-high non-small-cell lung cancer without a driver mutation, Resectable stage I to III non-small-cell lung cancer, Unresectable stage III non-small-cell lung cancer, Limited-stage small-cell lung cancer, Extensive-stage small-cell lung cancer, Lung neuroendocrine tumours (typical and atypical carcinoid), Thymic carcinoma
The commonest tumour of the anterior mediastinum in adults yet rare in absolute terms; most are found at stage I or II, and about a third of patients have myasthenia gravis.
- MRIStandard of care
Nothing recorded yet.
Nothing recorded yet.
Also on OnCo: Symptoms and red flags · Early detection roadmap.
Cases by country
No country-level case numbers. This cancer is not mapped to a GLOBOCAN site.
One section per setting: the options named, what each is for, the trials behind them, the recorded trade-offs and the questions to ask.
Contrast CT of the chest, acetylcholine receptor antibodies and neurology review; no biopsy of a resectable encapsulated mass; MRI to separate thymoma from cysts and hyperplasia.
Complete thymectomy with the tumour, by sternotomy or minimally invasive or robotic approaches for smaller tumours; en bloc resection of involved pericardium, lung or vessels for stage III.
Postoperative radiotherapy for stage III or incomplete resection; considered for stage II B2 to B3 tumours; observation for completely resected stage I and II type A to B1.
Induction chemotherapy with cisplatin, doxorubicin and cyclophosphamide (CAP) or a platinum doublet, then surgery or radiotherapy according to response.
Repeat resection of pleural recurrences where feasible; chemotherapy rechallenge; octreotide with prednisone for octreotide-scan-positive tumours; everolimus, sunitinib or lenvatinib; PD-1 antibodies avoided or given only in trials because of severe immune toxicity.
Subtypes & biomarkers
top- Type A thymoma (spindle cell, indolent, GTF2I mutant)
- Type AB thymoma (mixed, indolent, GTF2I mutant)
- Type B1 thymoma (lymphocyte-rich)
- Type B2 thymoma
- Type B3 thymoma (epithelial-rich, the most aggressive thymoma)
- Thymoma with myasthenia gravis or other paraneoplastic autoimmunity
- Micronodular thymoma with lymphoid stroma (rare, indolent)
- Stage III to IVA thymoma with pleural spread
- WHO histotype
- Masaoka-Koga and TNM stage
- Completeness of resection (R0, R1, R2)
- Acetylcholine receptor antibodies (myasthenia screen before surgery)
- GTF2I L424H mutation (type A and AB)
- Octreotide scan or somatostatin receptor PET (somatostatin analogue eligibility)
How often this target appears
- 1981Masaoka staging system published, later refined by Koga
- 1999WHO histological classification of thymic epithelial tumours (types A to C)
- 2014GTF2I L424H mutation found in most type A and AB thymomas
- 2017TNM staging for thymic tumours adopted in the eighth edition of the AJCC and UICC manuals
- 2018Everolimus phase 2 shows disease control in pretreated thymic epithelial tumours; severe immune toxicity of PD-1 antibodies in thymoma reported
Dated changes read from the records linked to this cancer: approvals, regulatory steps, reported trials, guideline versions and milestones. Newest first; no date is inferred.
All 6 changes by month →- 2026-09-18This recordThymoma (WHO types A, AB, B1, B2 and B3)Facts on this page last checked
When this page itself was last checked or edited.
- 2018MilestoneEverolimusEverolimus phase 2 shows disease control in pretreated thymic epithelial tumours; severe immune toxicity of PD-1 antibodies in thymoma reported
A milestone in how this cancer is treated.
- 2017MilestoneDisease-specific staging and risk systems (FIGO, Ann Arbor, IPI, R-ISS, ELN, IMDC)TNM staging for thymic tumours adopted in the eighth edition of the AJCC and UICC manuals
A milestone in how this cancer is treated.
- 2014MilestoneThymoma (WHO types A, AB, B1, B2 and B3)GTF2I L424H mutation found in most type A and AB thymomas
A milestone in how this cancer is treated.
- 1999MilestoneThymoma (WHO types A, AB, B1, B2 and B3)WHO histological classification of thymic epithelial tumours (types A to C)
A milestone in how this cancer is treated.
- 1981MilestoneDisease-specific staging and risk systems (FIGO, Ann Arbor, IPI, R-ISS, ELN, IMDC)Masaoka staging system published, later refined by Koga
A milestone in how this cancer is treated.
What is in development for Thymoma (WHO types A, AB, B1, B2 and B3), drawn from the whole corpus: 4 items. Drugs are grouped by the most advanced trial phase they have reached anywhere; approved treatments sit under standard of care. Technologies are the methods being tested for this cancer, trials are the studies recorded here, and ideas are proposals not yet in a trial.
Drugs in phase 3 · 1
Drugs in phase 2 · 1
Trials under way · 2
- A Study of KC1036 in Patients with Advanced Thymic Tumors · phase 2 · Beijing Konruns Pharmaceutical Co., Ltd.
- Target-Selected CAR-NK Cells (CD30, CD5, or Mesothelin) for Relapsed/Refractory B2 Thymoma or Thymic Carcinoma · phase 1/2 · Beijing Biotech
Open problems and what is being done
Randomised trials are almost absent; postoperative radiotherapy for stage II disease rests on registry data.
No systemic therapy is approved specifically for thymoma.
Autoimmune toxicity keeps checkpoint inhibitors off the table for most patients.
and how the field plans to fix it →What is being done about thisSide effects and quality of lifeAvailable now- CyclophosphamideApproved
- IMRT / IGRT (modern external beam)Standard of care
- Proton therapyEstablished
- Robotic & minimally invasive surgeryStandard of care
In trialsNothing recorded yet.
Ideas and roadmapsNothing recorded yet.
Background: Immune-related adverse events (irAEs). Also on OnCo: Side effects by symptom · Immune-related side effects · Toxicity compare · Survivorship planner.
Late recurrence a decade or more after surgery makes trial endpoints slow.
and how the field plans to fix it →What is being done about thisRecurrence and residual diseaseAvailable nowNothing recorded yet.
In trialsIdeas and roadmapsNothing recorded yet.
Also on OnCo: Treatment journeys · Survivorship planner.
Trials
topTrials recruiting now
Country and place are remembered in this browser only. A postcode is sent to OpenStreetMap's Nominatim service to find coordinates when you press the button; nothing else leaves your device.
Landmark trials
Expert centres
topExpert centres
Houston · cancer center | United States | 0 | 6,724 | 95,007 | #2 | ||
Seoul · hospital | South Korea | none recorded | 0 | 1,312 | 17,172 | #3 | |
Rochester, MN · hospital | United States | 0 | 4,511 | 44,748 | #5 | ||
Baltimore · cancer center | United States | 0 | 2,955 | 41,449 | #10 | ||
Berlin · university | Germany | none recorded | 0 | 1,563 | 17,749 | #12 | |
Boston · hospital | United States | 0 | 3,582 | 54,857 | #16 | ||
Heidelberg · cancer center | Germany | none recorded | 0 | 3,456 | 45,745 | #18 | |
Cleveland · hospital | United States | 0 | 2,264 | 29,412 | #20 | ||
Paris · cancer center | France | none recorded | 0 | 1,065 | 15,111 | #21 | |
Seoul · hospital | South Korea | none recorded | 0 | 464 | 3,248 | #22 | |
Manchester · cancer center | United Kingdom | none recorded | 0 | 104 | 2,145 | #23 | |
Shanghai · cancer center | China | none recorded | 0 | 1,678 | 18,354 | #55 | |
Philadelphia · cancer center | United States | 0 | 3,148 | 54,267 | - | ||
Ann Arbor, MI · cancer center | United States | 0 | 2,991 | 29,686 | - | ||
Shanghai · hospital | China | none recorded | 0 | 2,872 | 31,534 | - |
These are the things we can measure; they are not a ranking of quality. Each column is a field on the institution record or a count over what OnCo has linked; a centre that treats many patients with Thymoma but is thinly recorded here will look small.
Not known: OnCo holds no case-volume or outcome figures for centres, so none are shown. Where a national audit or registry publishes them, the centre's page links to it. Default order: Newsweek rank, then trials for this cancer, then research output.
Questions to ask
topQuestions to ask your oncologist about Thymoma
Newly diagnosed
- What is my exact diagnosis, stage, and grade, and which tests established them?Why: Everything else follows from an accurate stage and subtype.
- Which biomarkers have been tested on my tumour (for example WHO histotype, Masaoka-Koga and TNM stage, Completeness of resection, Acetylcholine receptor antibodies, GTF2I L424H mutation), and what were the results?Why: These results decide eligibility for targeted therapy, immunotherapy, and trials.
- Which subtype is my cancer, and does that change the recommended treatment?Why: Recognised subtypes for this cancer include Type A thymoma, Type AB thymoma, Type B1 thymoma.
- Is germline (inherited) genetic testing recommended for me or my family?Why: Inherited variants can change treatment and matter for relatives.
Diagnosis and staging
- For my situation (diagnosis and staging), which of the standard options do you recommend and why?Why: Guideline options include: Contrast CT of the chest, acetylcholine receptor antibodies and neurology review; no biopsy of a resectable encapsulated mass; MRI to separate thymoma from cysts and hyperplasia.
Resectable (stage I to III)
- For my situation (resectable (stage i to iii)), which of the standard options do you recommend and why?Why: Guideline options include: Complete thymectomy with the tumour, by sternotomy or minimally invasive or robotic approaches for smaller tumours; en bloc resection of involved pericardium, lung or vessels for stage III.
After surgery
- For my situation (after surgery), which of the standard options do you recommend and why?Why: Guideline options include: Postoperative radiotherapy for stage III or incomplete resection; considered for stage II B2 to B3 tumours; observation for completely resected stage I and II type A to B1.
Unresectable or bulky disease
- For my situation (unresectable or bulky disease), which of the standard options do you recommend and why?Why: Guideline options include: Induction chemotherapy with cisplatin, doxorubicin and cyclophosphamide (CAP) or a platinum doublet, then surgery or radiotherapy according to response.
- Am I a candidate for Cisplatin, Doxorubicin, Cyclophosphamide or related drugs, and what side effects should I expect?Why: Knowing the expected toxicities helps you plan work, family, and supportive care.
Recurrent or metastatic disease
- For my situation (recurrent or metastatic disease), which of the standard options do you recommend and why?Why: Guideline options include: Repeat resection of pleural recurrences where feasible; chemotherapy rechallenge; octreotide with prednisone for octreotide-scan-positive tumours; everolimus, sunitinib or lenvatinib; PD-1 antibodies avoided or given only in trials because of severe immune toxicity.
- Am I a candidate for Somatostatin analogues (octreotide, lanreotide), Everolimus, Sunitinib or related drugs, and what side effects should I expect?Why: Knowing the expected toxicities helps you plan work, family, and supportive care.
- How do the results of A Study of KC1036 in Patients with Advanced Thymic Tumors and Target-Selected CAR-NK Cells (CD30, CD5, or Mesothelin) for Relapsed/Refractory B2 Thymoma or Thymic Carcinoma apply to someone like me?Why: Trial populations differ from individual patients; ask how closely you match.
Any stage
- Are there clinical trials I could join, for example of Everolimus, Sunitinib, Lenvatinib, A Study of KC1036 in Patients with Advanced Thymic Tumors?Why: Trials are how the next standard of care is set; asking early keeps options open.
- Would a second opinion at a high-volume centre change anything, and can you help arrange it?Why: Rare or high-stakes decisions benefit from a centre that treats many similar patients.
- What supportive care (symptom control, nutrition, exercise, mental health, financial help) is available from the start?Why: Supportive care improves quality of life and helps patients complete treatment.
- I read that “Randomised trials are almost absent; postoperative radiotherapy for stage II disease rests on registry data”. How does that affect my plan?Why: Open problems are where trials and second opinions matter most.
- I read that “No systemic therapy is approved specifically for thymoma”. How does that affect my plan?Why: Open problems are where trials and second opinions matter most.
Newly diagnosed? Read the first 60 days with Thymoma, then print the one-page appointment sheet with room for the answers.
Print this page for your appointment (your browser's print command). These prompts are for discussion; your clinical team knows your case.
Direct links plus the targets, companies, and technologies of this cancer's products.
technologies
13targets
8drugs
11companies
8terms
2trials
2key papers
3The names on a thymic pathology report, and the sharp line between thymoma and thymic carcinoma that drives treatment, come from this classification.
The thymoma and thymic carcinoma pages follow this guideline for who gets surgery, radiotherapy and chemotherapy; its central message is that these rare tumours should be discussed in an expert network.
Whether a thymoma is called stage I or stage III, and hence whether radiotherapy follows surgery, still traces back to this scheme.
Latest papers
topQuery for this cancer: (TITLE:"Thymoma" OR ABSTRACT:"Thymoma" OR TITLE:"WHO types A, AB, B1, B2 and B3" OR ABSTRACT:"WHO types A, AB, B1, B2 and B3" OR TITLE:"Type A thymoma" OR ABSTRACT:"Type A thymoma" OR TITLE:"Type AB thymoma" OR ABSTRACT:"Type AB thymoma" OR TITLE:"Type B thymoma" OR ABSTRACT:"Type B thymoma" OR TITLE:"Thymoma with myasthenia gravis" OR ABSTRACT:"Thymoma with myasthenia gravis") AND (treatment OR therapy OR trial OR survival OR diagnosis). Results are unfiltered search hits about Thymoma (WHO types A, AB, B1, B2 and B3), not a curated reading list.
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