Place the mass in the prevascular, visceral or paravertebral compartment (ITMIG), then read its content — fat, fluid, calcification, enhancement — which narrows prevascular masses to thymic lesions, lymphoma, germ cell tumours and thyroid.
Orient first
- Prevascular: thymoma, thymic cyst and hyperplasia, lymphoma, germ cell tumours, retrosternal thyroid.
- Visceral: nodes, foregut duplication cysts, oesophageal lesions, vascular.
- Paravertebral: neurogenic tumours (schwannoma, neurofibroma, ganglioneuroma), extramedullary haematopoiesis.
Acquire the study
- Contrast-enhanced CT chest with coronal and sagittal reformats.
The manoeuvre
- Compartment on axial and sagittal reformats (ITMIG boundaries).
- Attenuation in HU: fat, fluid (0–20 HU), calcification, enhancement.
- Invasion of vessels, pericardium, lung; pleural drop metastases (thymoma).
- Size in cm; nodes elsewhere (lymphoma).
What confirms it
- A compartment and content pattern that fits a named entity; tissue when solid.
What licenses you to exclude it
- A cyst or hyperplasia on MRI needs no biopsy.
The classic misread
- Calling a thymic cyst with high-protein content solid on CT — MRI shows it is a cyst.