# Type A and type AB thymoma

Source: https://onco.cc/cancers/thymoma-type-a-ab/  
OnCo record `thymoma-type-a-ab` (Cancer). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Type A and type AB thymoma are the indolent end of thymoma, tumours of the thymus gland made of spindle-shaped epithelial cells (type A) or mixed with lymphocyte-rich areas (type AB), mostly in older adults and driven by a GTF2I mutation. Nine in ten are found at an early stage and almost none come back after complete surgery, so surgery alone is usually the whole treatment.

## Summary

The WHO classification of thymic tumours divides thymoma into types A, AB, B1, B2 and B3 (with rare others), and the ITMIG consensus refined the criteria at the A/AB borderland and proposed the term atypical type A thymoma for tumours with increased mitoses or necrosis (Marx 2014). In the worldwide database, type A made up 12 percent and, with type AB, occurred at a higher age (64 and 57 years); 90 percent of type A were stage I or II, and recurrence after resection was 1 to 2 percent for types A and AB against 2 to 7 percent for B1 to B3 (Weis 2015). The GTF2I L424H mutation, characteristic of types A and AB, is recorded on the parent page. Atypical type A components can rarely metastasise, as in a case with lung and brain metastases 10 and 15 years after diagnosis (Journal of Thoracic Disease 2017).

How it differs from its parent: the parent page covers all thymoma types and their staging; types A and AB are the oldest patients, the earliest stages, the lowest recurrence and the GTF2I-mutant biology, and paraneoplastic myasthenia gravis is less frequent than with the B types.

How common: about 12 percent (type A) of thymomas, with type AB a further large share (Weis 2015).

Treatment: complete surgical resection; postoperative radiotherapy only for incompletely resected or stage III disease as on the parent page; systemic therapy is rarely needed and follows the parent's platinum-based regimens when it is.

## Fields

- Kind: Cancer
- Last checked: 2026-09-24
- Also known as: Type A thymoma; Type AB thymoma; Spindle cell thymoma; Mixed thymoma; Atypical type A thymoma; Type A thymoma (spindle cell, indolent, GTF2I mutant); Type AB thymoma (mixed, indolent, GTF2I mutant)
- Tags: subtype-page; wave4; rare
- Group: thoracic
- Burden: Type A is the least common thymoma at 12 percent of 4,221 thymomas in the ITMIG worldwide database, with type AB also common in Europe and the United States and both rarer in Asia; patients are older (64 and 57 years) than with other thymomas (Weis 2015).
- Subtypes: Type A thymoma (spindle or oval cells, few lymphocytes; 90 percent stage I or II); Atypical type A thymoma (increased mitoses or necrosis; rare metastasis); Type AB thymoma (type A areas mixed with lymphocyte-rich type B-like areas)
- Biomarkers: WHO histotype on ITMIG criteria; GTF2I L424H mutation; Masaoka-Koga or TNM stage and resection status; Acetylcholine receptor antibodies (myasthenia gravis)

## Sections of this record

The page is a hub with ten sections in reading order; large sections have their own page. The same plan as JSON: https://onco.cc/api/v1/cancers/thymoma-type-a-ab/sections.json

- Overview (on the hub): The TL;DR, the family this cancer belongs to, the organ, who gets it and what the state of the art is. https://onco.cc/cancers/thymoma-type-a-ab/#overview
- What it is (on the hub): Anatomy, the subtypes and how they differ, how it is staged, and where advanced disease spreads. https://onco.cc/cancers/thymoma-type-a-ab/#what-it-is [3 subtypes]
- Finding it (on the hub): How it shows itself, how it is confirmed, what screening exists, and the biomarkers clinicians test for. https://onco.cc/cancers/thymoma-type-a-ab/#finding-it [4 biomarkers]
- Treating it (on the hub): The standard of care by setting, the medicines, surgery and radiotherapy named in it, and the regimens behind them. https://onco.cc/cancers/thymoma-type-a-ab/#treating-it [1 setting]
- Evidence (on the hub): Trials recruiting now, the landmark trials, the key papers and what they mean, the latest literature, and the milestones year by year. https://onco.cc/cancers/thymoma-type-a-ab/#evidence
- The science (on the hub): The molecular landscape: the targets and how often each appears, the pathways, the mechanics stages and the preclinical models. https://onco.cc/cancers/thymoma-type-a-ab/#science
- Where you are (own page): Cases by country, the UK and NHS pathway and other country lenses, and the expert centres with trials on record. https://onco.cc/cancers/thymoma-type-a-ab/where-you-are/
- Living with it (on the hub): The decisions you may face, the aids that walk through them, the warnings on record, the first sixty days and the questions to ask. https://onco.cc/cancers/thymoma-type-a-ab/#living-with-it [7 questions]
- What is coming (own page): Everything in development, the open problems and what is being done about them, the roadmaps, and what changed on this record. https://onco.cc/cancers/thymoma-type-a-ab/coming/
- Data (own page): Every connected record, the notes, the JSON, Markdown and RDF twins, and where the record came from and when it was checked. https://onco.cc/cancers/thymoma-type-a-ab/data/

## Standard of care

- All stages: Complete resection; postoperative radiotherapy for incomplete resection or stage III as on the parent page; systemic therapy rarely needed. ([Thymoma (WHO types A, AB, B1, B2 and B3)](https://onco.cc/cancers/thymoma/), [Thymoma and thymic carcinoma](https://onco.cc/cancers/thymic-epithelial/))

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Thymoma
- NCI PDQ: thymoma and thymic carcinoma treatment: https://www.cancer.gov/types/thymus-cancer/thymoma-thymic-carcinoma
- Weis 2015, JTO: the impact of thymoma histotype on prognosis in the ITMIG worldwide database, 4,221 thymomas: https://doi.org/10.1097/jto.0000000000000393
- Marx 2014, JTO: ITMIG consensus on the use of the WHO histological classification of thymoma and thymic carcinoma: https://doi.org/10.1097/jto.0000000000000154
- Journal of Thoracic Disease 2017: AB thymoma with atypical type A component and delayed lung and brain metastases: https://doi.org/10.21037/jtd.2017.07.95

## Connected records

- cancers: [Micronodular thymoma with lymphoid stroma](https://onco.cc/cancers/micronodular-thymoma/), [Thymoma (WHO types A, AB, B1, B2 and B3)](https://onco.cc/cancers/thymoma/), [Thymoma and thymic carcinoma](https://onco.cc/cancers/thymic-epithelial/), [Type B1 and type B2 thymoma](https://onco.cc/cancers/thymoma-type-b1-b2/), [Type B3 thymoma](https://onco.cc/cancers/thymoma-type-b3/)

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JSON: https://onco.cc/api/v1/entities/thymoma-type-a-ab.json