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Type B1 and type B2 thymoma are thymus gland tumours in which the epithelial tumour cells are mixed with many immature lymphocytes, resembling the normal thymic cortex; B2 is the commonest thymoma of all. They are strongly linked to myasthenia gravis, are usually cured by surgery, and get radiotherapy when they have grown beyond the gland or could not be fully removed.
Types B1 and B2 sit between the indolent A and AB thymomas and the aggressive B3 in the WHO classification; B1 resembles normal thymic cortex with sparse epithelial cells and B2 has clusters of epithelial cells among the lymphocytes, and the ITMIG consensus set criteria for distinguishing B1, B2 and B3 (Marx 2014). In the worldwide database type B2 was the most common histotype (28 percent), the B types presented at higher stages than A and AB, and recurrence after resection for B1 to B3 was 2 to 7 percent, with age, stage and resection status the multivariate predictors of survival and histology affecting recurrence (Weis 2015). Myasthenia gravis and other paraneoplastic autoimmunity are most frequent with the B types.
How it differs from its parent: the lymphocyte-rich histology can be mistaken for lymphoma or normal thymus on biopsy, the association with myasthenia gravis shapes perioperative care, and the B types more often present at Masaoka-Koga stage II or III than types A and AB.
How common: B2 is 28 percent of thymomas, the largest share (Weis 2015).
Treatment: complete resection with or without preoperative therapy for locally advanced disease; postoperative radiotherapy for stage III or incomplete resection; platinum-based chemotherapy (cisplatin, doxorubicin, cyclophosphamide) for unresectable or metastatic disease, as on the parent page; myasthenia gravis managed jointly with neurology.
Type B2 is the most common thymoma at 28 percent of 4,221 thymomas in the ITMIG worldwide database; B1 and B2 are more frequent in Asia than types A and AB (Weis 2015).
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.
Same organ: Mediastinal germ cell tumour, Pleuropulmonary blastoma (types I, Ir, II and III), Type A and type AB thymoma, Type B3 thymoma, Micronodular thymoma with lymphoid stroma, Adenocarcinoma of the lung, Squamous cell carcinoma of the lung, Large cell carcinoma of the lung, Sarcomatoid carcinoma of the lung, Adenosquamous carcinoma of the lung, Invasive mucinous adenocarcinoma of the lung, Adenocarcinoma in situ and minimally invasive adenocarcinoma of the lung, Basaloid squamous cell carcinoma of the lung, Lymphoepithelial carcinoma of the lung, Pulmonary blastoma (adult), 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), Thymoma (WHO types A, AB, B1, B2 and B3), Thymic carcinoma
Complete resection; postoperative radiotherapy for stage III or incomplete resection; platinum-based chemotherapy for unresectable or metastatic disease, as on the parent page.
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Query for this cancer: (TITLE:"Type B1 and type B2 thymoma" OR ABSTRACT:"Type B1 and type B2 thymoma" OR TITLE:"Type B1 thymoma" OR ABSTRACT:"Type B1 thymoma" OR TITLE:"Type B2 thymoma" OR ABSTRACT:"Type B2 thymoma" OR TITLE:"Lymphocyte-rich thymoma" OR ABSTRACT:"Lymphocyte-rich thymoma" OR TITLE:"Cortical thymoma" OR ABSTRACT:"Cortical thymoma" OR TITLE:"Type B1 thymoma lymphocyte-rich" OR ABSTRACT:"Type B1 thymoma lymphocyte-rich") AND (treatment OR therapy OR trial OR survival OR diagnosis). Results are unfiltered search hits about Type B1 and type B2 thymoma, not a curated reading list.
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Bleeding that will not stop, black or bloody stools, or unexplained bruising when platelets are expected to be low.
Cumulative dose: risk rises steeply above 400-550 mg/m² (see the anthracycline calculator).
Dose reduce or avoid for CrCl below 60 (carboplatin is the alternative).
Reduce by 50% for bilirubin 20-50 µmol/L and 75% for 50-85 µmol/L.
Heart damage from cancer treatment: anthracyclines weaken the heart muscle permanently in a dose-related way, trastuzumab does so reversibly, and some kinase inhibitors raise blood pressure or disturb rhythm. Heart function (LVEF) is monitored by ultrasound during treatment.
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