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Anterior mediastinal mass (the 4 T’s)
ChestCT / MRI
A prevascular (anterior) compartment mass. The classic "4 T’s" (thymic, teratoma/germ cell, thyroid, terrible lymphoma) plus age and tumour markers direct work-up.
Differential
Thymoma
common- •Well-defined, often mildly lobulated soft-tissue mass
- •Adult >40 y; association with myasthenia gravis
- •Capsular breach / pleural drop metastases if invasive
Lymphoma (Hodgkin / primary mediastinal B-cell)
common- •Lobulated mass encasing vessels, often bulky
- •Young adult, B symptoms
- •Additional nodal disease, FDG-avid
Germ cell tumour / teratoma
less-common- •Fat, fluid and calcification/tooth in mature teratoma
- •Young male; elevated AFP/β-hCG in malignant types
Retrosternal (thyroid) goitre
less-common- •Continuity with the cervical thyroid
- •High native CT attenuation, avid enhancement, calcification
- •Tracheal displacement
Thymic hyperplasia
rare- •Diffuse enlargement retaining thymic shape
- •Chemical-shift signal drop on in/opposed-phase MRI
- •Rebound after chemotherapy/stress
Thymic cyst
rare- •Simple fluid attenuation, imperceptible wall, no enhancement
Key discriminators
- •Patient age (thymoma older; lymphoma/germ cell younger)
- •Fat/calcification (teratoma) vs homogeneous soft tissue
- •Continuity with thyroid gland
- •Tumour markers (AFP, β-hCG)
- •Chemical-shift signal drop (thymic hyperplasia)
Work-up / next steps
- 1.Contrast CT to localise compartment and characterise tissue
- 2.Serum AFP and β-hCG in young patients
- 3.MRI chemical-shift imaging for suspected thymic hyperplasia
- 4.Biopsy for lymphoma; surgical resection for suspected thymoma
References
- Carter BW et al. ITMIG mediastinal compartment classification. RadioGraphics.
- Radiopaedia: Anterior mediastinal mass.
Educational clinical decision support only. This differential does not make a diagnosis, is not a medical device, and must never substitute for interpretation by a qualified radiologist correlated with the full clinical picture and prior imaging.