# Mediastinal Masses Differential

> Mediastinal masses for NEET-PG Surgery: anterior 4 Ts, middle compartment cysts, posterior neurogenic tumours, ITMIG zones and biopsy rules.

- Canonical URL: https://prepelephant.com/topics/neet-pg/surgery/mediastinal-masses
- Exam / course: NEET-PG · Subject: Surgery
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Mediastinal Masses Differential", PrepElephant, https://prepelephant.com/topics/neet-pg/surgery/mediastinal-masses

## Direct answer

Which compartment the mass sits in shortens a mediastinal differential from dozens of entities to two or three. Anterior (before the pericardium): the "4 Ts" — Thymoma, Teratoma and other germ cell tumours, Terrible lymphoma, and Thyroid (retrosternal goitre) — plus parathyroid adenoma. Middle: bronchogenic and pericardial cysts, lymphadenopathy (lymphoma, metastases, tuberculosis in India) and mediastinal extensions of lung tumours. Posterior: neurogenic tumours — schwannoma and neurofibroma from nerve sheath, ganglioneuroma and neuroblastoma from sympathetic ganglia in children — plus enteric duplication cysts. Age and symptoms refine it (neuroblastoma in a child, teratoma in a young adult, lymphoma with systemic features, thymoma with myasthenia), tumour markers may spare a biopsy (elevated AFP or beta-hCG in mediastinal germ cell tumour means chemotherapy, not excision), and the surgeon's rule is that lymphoma and germ cell tumours are biopsied — usually via VATS or image-guided core — while thymoma, cysts and neurogenic tumours are resected.

## What you must remember

- Compartment anatomy: classical radiological divisions on lateral chest X-ray/CT — anterior (between sternum and pericardium/brachiocephalic vessels), middle (pericardial and its reflections), posterior (behind pericardium, paravertebral gutters); the newer ITMIG scheme redefines boundaries but compartment-first thinking still drives the exam answer.
- Anterior compartment detail: thymoma is the commonest anterior mediastinal tumour in adults; teratodermoids contain fat, calcification and teeth/hair on CT; Hodgkin and non-Hodgkin lymphoma (and in India tuberculous nodes); substernal goitre (continuous with the cervical gland, enhances like thyroid, may show retrosternal extension on plain films with tracheal displacement).
- Middle compartment: pericardial cysts (right cardiophrenic angle "spring water" cyst), bronchogenic cysts (subcarinal or paratracheal, fluid density, may compress airway), foregut duplication cysts.
- Posterior compartment: neurilemmoma (schwannoma) and neurofibroma (nerve sheath, adults, dumb-bell shape if they extend through the intervertebral foramen — always get MRI to exclude intradural extension); ganglioneuroma (older child, asymptomatic); neuroblastoma (under 5 years, metastatic, urinary catecholamines); paraganglioma.
- Workup: contrast CT (fat, fluid, calcification, enhancement answer most questions), MRI for neurogenic extension and vascular invasion, thyroid function and uptake if goitre suspected, serum AFP and beta-hCG for suspected nonseminomatous germ cell tumour, and myasthenia serology with a thymic mass.
- Golden management rule: biopsy (VATS, Chamberlain procedure/anterior mediastinotomy, image-guided) for lymphoma and germ cell tumours — resection does not help and may complicate later chemotherapy; resection for thymoma, cysts, encysted empyema mimics, goitre and neurogenic tumours; observational follow-up for small asymptomatic cysts.

## How to reason through a case

A 34-year-old man has a routine pre-employment chest radiograph that shows a widened mediastinum; CT demonstrates a well-defined anterior mediastinal mass with fat density and a calcified nodule. Reason by compartment and content: anterior mass with fat and calcification in a young adult is a mature teratoma (dermoid cyst) — a resectional diagnosis, so he is scheduled for excision (via median sternotomy or VATS depending on size) without biopsy, since biopsy of a teratoma only risks spillage. Now change one variable: the mass is homogeneous and soft tissue density with mediastinal nodes and the patient has night sweats — that is lymphoma territory; the next step is core biopsy or VATS biopsy for histology and immunophenotyping, not excision, because treatment is chemotherapy. Change it again: a 26-year-old man has a bulky anterior mass with gynaecomastia and serum AFP in the thousands — nonseminomatous germ cell tumour; the marker itself is diagnostic, biopsy is avoidable (bleeding and tumour seeding risks), and treatment is platinum-based chemotherapy with residual mass resection afterwards. And a 50-year-old with ptosis and diplopia plus an anterior lobular mass is a thymoma until excised with the whole thymus after myasthenia workup. One posterior example completes the map: a 29-year-old woman with a paravertebral mass and intercostal neuralgia — MRI before any surgery to map a dumb-bell schwannoma, because missing intradural extension turns a routine thoracotomy into an unplanned neurosurgical emergency.

## Where students slip

The classic slip is calling every posterior mediastinal mass "neurofibroma" — the exam expects the split into nerve sheath tumours (adults: schwannoma more than neurofibroma) versus sympathetic chain tumours (children: neuroblastoma under 5, ganglioneuroma older) with the age clue. The second is excising what should be biopsied: lymphoma and nonseminomatous germ cell tumour are chemotherapy diseases, and the anterior mediastinotomy (Chamberlain) or VATS biopsy exists precisely for them. Third, forgetting MRI for the posterior mass with a neurological sign — the intraspinal component must be excluded before the thoracic operation.

## Frequently asked questions

### What are the "4 Ts" of the anterior mediastinum?
Thymoma, Teratoma (germ cell tumours), Terrible lymphoma and Thyroid (retrosternal goitre) — with parathyroid adenoma a fifth classic anterior entity.

### Which tumours characteristically occupy the posterior mediastinum?
Neurogenic tumours — schwannoma and neurofibroma from nerve sheaths, ganglioneuroma and neuroblastoma from sympathetic ganglia — plus enteric duplication cysts.

### Which mediastinal masses are biopsied rather than excised?
Lymphoma and nonseminomatous germ cell tumours — they are treated with chemotherapy; elevated AFP or beta-hCG may itself establish the diagnosis and spare a biopsy.

### Which clinical syndrome accompanies thymoma most classically?
Myasthenia gravis — roughly a third to half of thymoma patients have it, and any thymic mass warrants myasthenia assessment before surgery.