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10 slides generated from the cancer page, with a quiz from the open benchmark and speaker notes that cite the sources. Arrow keys move between slides; Print gives one slide per page.
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.
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.
| Setting | Approach | Guideline |
|---|---|---|
| Diagnosis and staging | 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. | not mapped |
| Resectable (stage I to III) | 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. | not mapped |
| After surgery | 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. | not mapped |
| Unresectable or bulky disease | Induction chemotherapy with cisplatin, doxorubicin and cyclophosphamide (CAP) or a platinum doublet, then surgery or radiotherapy according to response. | not mapped |
| Recurrent or metastatic disease | 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. | not mapped |