INTRODUCTION

MEDIASTINUM is the central compartment in the thoracic cavity between the two lungs Any age group-both sexes (often on routine x ray) (50% are asymptomatic)

ANATOMY

• Anteriorly : Sternum• Posteriorly : Thoracic vertebrae• Superiorly : Plane of thoracic inlet• Inferiorly : Diaphragm• Laterally : Mediastinal pleura

CROSS SECTION

Anterior - 1 Middle - 2 Posterior - 3

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SUPERIOR MEDIASTINUM MUSCLES : Origins of sternohyoid ,sternothyroid,lower ends of

longus colli ARTERIES : aortic arch,brachiocephalic artery,thoracic portions

of left common carotid, and left subclavian artery VEINS : brachiocephalic vein,upper part of SVC,left highest

intercostal vein NERVES : vagus,superficial and deep cardiac plexus,phrenic

nerve,left recurrent larnygeal nerve Trachea Oesophagus Thoracic duct Remains of thymus lymph glands

ANTERIOR MEDIASTINUM Loose areolar tissue Some lymphatic vessels which arise from the

convex surface of the liver 2 or 3 mediastinal lymph nodes small mediastinal branches of internal mammary

artery Thymus

MIDDLE MEDIASTINUM

PericardiumHeartDescending aortaLower half of SVC and azygous veinsRight and left pulmonary veinsTracheaTrachea BifurcationMain BronchiPhrenic NerveHilar Lymph NodePericardiophrenic vessels

POSTERIOR Esophagus Vagus Splanchnic nerves Thoracic duct Thoracic descending Aorta Azygos Vein and accessory hemiazygous vein Hemi-azygos vein Paravertebral Lymph node

CLASSIFICATION - ANATOMICALANTEROSUPERIOR: - Thymic neoplasms - Cysts - Mesenchymal - Lymphomas - Germ cell tumours - Carcinoma - Endocrine MIDDLE: - Cysts - Mesenchymal - Lymphomas - Carcinoma POSTERIOR MEDIASTINAL: - Neurogenic - Mesenchymal - Cysts - Endocrine

CLASSIFICATION- PATHOLOGICAL NEUROGENIC TUMOURS - MOST COMMON : NEUROFIBROMA, NEURILEMOMA, GANGLIONEUROMA, NEUROBLASTOMA, NEUROSARCOMA OTHERS : CHEMODECTOMA, PARAGANGLIOMA

• THYMOMA - BENIGN, MALIGNANT• LYMPHOMA – HODGKINSDISEASE , • T AND B IMMUNOBLASTIC SARCOMA,

SCLEROSING FOLLICULAR CELL• GERM CELL TUMOURS- ,

TERATODERMOID(BENIGN AND MALIGNANT) SEMINOMA, NONSEMINOMA (EMBRYONAL,CHORIOCARCINOMA,ENDODERMAL )

• MESENCHYMAL TUMOURS – • FIBROMA,/FIBROSARCOMA,LIPOMA/ LIPOSARCOMA,

LEIOMYOMA/LEIOMYOSARCOMA, RHABDOMYOSARCOMA,MYXOMA, MESOTHELIOMA,XANTHOGRANULOMA, HEMANGIOMA,HEMANGIOENDOTHELIOMA,HEMANGIOPERICYTOMA LYMHANGIOMA,LYMPHANGIOMYOMA,,LYMPHANGIOPERICYTOMA

• ENDOCRINE – INTRATHORACIC THYROID,PARATHYROID ADENOMA/CARCINOMA CARCINOID

• CYSTS – BRONCHOGENIC, PERICARDIAL, ENTERIC, THYMIC, THORACIC DUCT NONSPECIFIC

• GIANT LYMPH NODE HYPERPLASIA – CASTLEMAN'S DISEASE• CHONDROMA• EXTRAMEDULLARY HEMATOPOIESIS

Common Pathologies• ANTEROSUPERIOR MEDIASTINUM - THYMIC NEOPLASM-33% LYMPHOMA-19% GERM CELL TUMOUR-17%• MIDDLE MEDIASTINUM - CYSTS-61%,LYMPHOMA-21%• POSTERIOR MEDIASTINUM - NEUROGENIC-53%,CYST-32%

CHILDREN

Posterior Mediastinum Most often benign 2/3 of tumors symptomatic

Neurogenic tumors(40%)Lymphoma(18%)Cysts(18%)Germ cell tumors(11%)Mesenchymal tumors(9%)Thymomas -Rare

ADULTS

Anterior Mediastinum Often Malignant Ages 30 – 50 1/3 of tumors are symptomatic

Neurogenic tumours(21%)Cysts(20%)Thymomas(19%)Lymphoma(13%)Germ cell tumours(11%)Mesenchymal tumours(7%)Endocrine tumours(6%)

MALIGNANCY

All tumors 25% Per Section

Anterior Superior 59% Posterior 16% Middle 16%

Symptoms Chest pain Dyspnea Cough Fever Weight loss Fatigue Dysphagia Night sweats

Clinical Features

SVC syndromeMyasthenia gravis, Immune deficiency, Aplastic anemia - ThymomaSympathetic ganglion - Horner’s SyndromeIn late stages : Diaphragmatic palsyPleural EffusionHaemorrage (Erosion of major vessels)

Malignant Tumors Invasion Structure

Tracheobronchial tree and lungs Esophagus Superior Vena Cava Pleura and Chest Wall Intrathoracic nerves

CLINICAL MANIFESTATIONS OF ANATOMIC COMPRESSION OR INVASION BY NEOPLASMS OF THE MEDIASTINUM

Vena caval obstruction Pericardial tamponadeCongestive heart failureDysrhythmiasPulmonary stenosisTracheal compressionEsophageal compressionVocal cord paralysisPostobstructive pneumonitis

Horner's syndrome

Phrenic nerve paralysis

Chylothorax

Chylopericardium

Spinalcord compressive syndrome

Pancoast's syndrome

DIAGNOSTIC EVALUATION History and Physical examination Radiology - Standard chest films ,Barium swallow, Fluroscopy ,Arteriography,Venography, CT,MRI,USG,Myelography Radioisotope scanning SerologyEndoscopy Bronchoscopy Needle aspiration and biopsy Operative procedures – Mediastinoscopy, Mediastinotomy Thoracotomy

ULTRASTUCTURAL CHARACTERISTICS OF MEDIASTINAL TUMOURS

Carcinoid : Dense core granules,fewer tonofilaments and desmosomes

Lymphomas : Absence of junctional attatchments and epithelial features

Thymoma : Well formed desmosomes ,bundles of tonofilaments

Germ cell : Prominent nucleoli ,even chromatin, scant desmosomes, rare tonofilaments

Neuroblastoma :Neurosecretory granules ,synaptic endings

Treatment Thoracotomy and removal If malignant - Adjuvant therapy like radiotherapy & chemotherapy Sternotomy - Sup. and ant.tumours

Thymic cancers require surgery, followed by radiation or chemotherapy. Types of surgery include thoracoscopy (a minimally invasive approach), mediastinoscopy (minimally invasive) and thoracotomy (a procedure performed through an incision in the chest).

Lymphomas are recommended to be treated with chemotherapy followed by radiation.

Neurogenic tumors found in the posterior (back) mediastinum are treated surgically.

THYMOMAS Most common tumour of the anterosuperior mediastinum in adults Fifth to Sixth decade Both sexes are equally affected

Types HISTOLOGY: Epithelial cell - Poor prognosis Lymphocytic Mixed Spindle - Better prognosis

50% THYMOMAS ARE MALIGNANT

Clinical features: ASYMPTOMATIC 50% 30 - 40% ASSOCIATED WITH MYASTHENIA GRAVIS Chest pain Dysphagia Dyspnoea SVC obstruction

Modified Masaoka clinical staging of thymoma

Stage DefinitionI Macroscopically and microscopically completely encapsulatedIIA Microscopic transcapsular invasionIIB Macroscopic invasion into surrounding fatty tissue or grossly adherent to but not through

mediastinal pleura or pericardiumIII Macroscopic invasion into neighboring organs (ie, pericardium, great vessels, or lung)IVA Pleural or pericardial disseminationIVB Lymphogenous or hematogenous metastasis

Investigations

Chest Xray : Lateral view - Opacity in mediastinum

Mediastinoscopy & biopsy. Tensilon Diagnostic test : Injecting 10mg

edrophonium chloride iv. Myasthenia is relieved within 1 min temporarily

CT scan

Treat myasthenia - Neostigmine

Thymectomy IS BENEFICIAL in: Disease < 5yrs Myasthenia without thymoma In young females

Treatment

Surgical removal of the tumor is the preferred treatment. Surgery is often the only treatment required for stage I tumors. Treatment of thymoma often relieves the symptoms caused by paraneoplastic syndromes. Stages II, III, and IV thymomas are often treated with surgery and some form of adjuvant therapy.

RETROSTERNAL GOITRE

> 50 % goitre below the suprasternal notch. PRIMARY : rare (1%) -SECONDARY : common

PRIMARY Arises from ectopic thyroid tissue from mediastinum. It gets it blood supply from mediastinum itself,not from the neck.Not related to existing thyroid tissue in the neck

SECONDARY

Extension from an enlarged thyroid from the neck Arises from lower pole of a nodular goitre usually. Commonly seen in short neck or obese individuals Nodule gets drawn into the superior medistinum due To negative intrathoracic pressure

TYPES Substernal type : part of the nodule is palpable in

the lower neck Plunging goitre : an intrathoracic goitre is

occasionally forced into the neck by increased intrathoracic pressure

Intrathoracic goitre: neck is normal

CLINICAL FEATURES SYMPTOMS :Dyspnoea Cough and stridorDysphagiaSIGNS :Engorgement of neck veins and superficial veins on the chest wallLower border is not seen on inspection and not felt on palpation

PEMBERTON'S SIGN : is positive Percussion :dull note over sternum Can be nodular,toxic or malignant Rarely – recurent larygeal nerve palsy

INVESTIGATIONS

Chest X -ray CT scan and MRI is diagnostic

TREATMENT Surgical removal Commonly through incision in neck Large goitre or malignant type median sternotomy

is required rarely

Radiodine therapy is not not accepted Stridor –due to compression of tracheobronchial

tree it is very dangerous, as often it is not possible to clear airway either by intubation or tracheostomy

Surgical removal should be complete : recurrence – very difficult to operate

Neurogenic tumors

Neurofibroma,NeurilemmoasMelanotic schwannoma

Ganglioneuromas

Chemodectoma Pheochromocytomas

Benign Malignant

Neurofibrosarcomas

GanglioneuroblastomaNeuroblastomas

Malignant chemodectomaMalignant Pheochromocytoma

Neurilemmomas

Most common

Arises from the Schwann cells of the nerve sheathWell encapsulated

X-ray :dense homogenous mass in the posterior mediastinumSurgical excision

Neurofibromas

Arises from the nerve sheath and nerve fibres Poorly encapsulated

Treatment :Difficult to excise due to its infiltrating natureMultiagent chemotherapy due to aggressive nature

Ganglioneuromas

Originates from sympathetic chain Composed of ganglionic cells and nerve fibresMore common in children Mostly asymptomaticUsual location is paravetebral regionINVESTIGATION: X ray- well marginated lesion on

anterolateral aspect of spine TREATMENT: surgical resection

Neuroblastomas

Usually seen among young childrenMost poorly differentiated tumor Arising from the sympathetic nervesHighly invasive tumor 75% -children clinical feature is fever cough

diarrhea vomitingAt time of presentation – pain,neurological defects,Horners

syndrome,respiratory distress ataxia-lymph node metastasis Metastasis to spinal cordInvestigation : CT,MRI,radionucleide imagingTreatment :Radiotherapy and chemotherapy

Germ cell tumors

Benign Malignant

Seminomatous Non seminomatous

Choriocarcinomas

Embryonal carcinomas

Mixed tumors

Teratocarcinomas

Yolk sac carcinomas.

LAB STUDIES

Beta human chorionic gonadotropin

Alpha-fetoprotein

IMAGING

Chest radiography

CT scan of the chest and mediastinum

DIAGNOSTIC PROCEDURES

Transthoracic needle biopsy

Cervical mediastinoscopy and substernal extended mediastinoscopy

Anterior mediastinotomy

Video-assisted thoracoscopy

Sternotomy and thoracotomy

TERATOMA is the commonest. Symptoms: usually asymptomatic, cough, dyspnoea and chest pain can

occur. Investigations : Chest Xray, CT, MRI Treatment: complete surgical excision and chemotherapy.

SEMINOMA: 25- 50% of GCT Men 20- 40 yrs Symptoms: dysnoea, substernal pain, weakness, gynaecomastia, SVC

syndrome Investigations: chest Xray, CT, Treatment: radiotherapy

Non Seminoma: Embryonal cell carcinoma, endodermal thymus

tumours, choriocarcinoma, yolk sac tumours with multiple cellular components.

Symptoms: chest pain, hemoptysis, cough, fever, wt loss, gynaecomastia

Investigation: AFP, beta HCG are increased. Treatment: chemotherapy with bleomycin,

etoposide and cisplatin If there is residual tumour then = surgery

Lymphomas

Commonly situated in anterior mediastinumCommonest Hodgkin's lymphomasCommon in 40-60 yrsNon Hodgkin’s affects any age. Symptoms: fever, wt loss, night sweats, compressive

symtoms like pain, dyspnoea, wheezing, SVC syndrome and pleural effusion.

Investigations : x-ray , CT scan, cervical lymph node biopsyTreatment: Combination chemotherapySurgery not usually done.

Vascular and Lymphatics

Hemangiomas Lymphangiomas HaemangimyomasLymphangimyomas

Commonest is lymphangioma(cystic hygroma)Seen in ant mediastinum

Mediastinal cysts

Primary cystPericardial cyst

Bronchogenic cystEnteric cystThymic cyst

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