Mediastinal Tumors
 

Mediastinum

Central cavity of the thorax

Sides         : pleural cavities (parietal pleura)

Inferior       : diaphragm

Superior     : thoracic inlet

Anterior      : sternum

Posterior    : vertebral body

No compartment of body carries more physiologic traffic.

 

 

 

 

Compartments

Superior

Superiorly, the fascial planes communicate with the neck à Infection spreading

Anterior

Anterior      : sternum

Posterior    : upper dorsal spine

Inferior       : anterior border of heart

Middle

Superior     : anterior border of heart

Inferior       : diaphragmatic surface

Posterior    : anterior border of dorsal spine

Posterior

 

 

 

Contents

Anterior-Superior : thymus gland, aortic arch, SVC, internal mammary vessels, lymph node,  parathyroid gland, ectopic thyroid tissue.

Middle : pericardium, heart, great vessels, trachea, tracheal bifurcation, main bronchi, phrenic nerve, hilar lymph node.

Posterior :  esophagus, vagus nerves, sympathetic chain, thoracic duct, thoracic desending aorta, azygos and hemiazygos vein, paravertebral lymph node.

 

Tumors and Cysts

25% are primary cystic lesions.

Thymic neoplasm is the most common primary tumor.

Lymphoma, neurogenic, germ cell tumors are common tumor.

In childhood series, malignancy could be found 50% of tumors, which are Hodgkins disease or Non-Hodgkin Lymphoma.

Lymphoma is the most common malignancy in all age.

 

Clinical Manifestations

1/3 of Patients are asymptomatic.

Most common symptoms are nonspecific (chest pain, cough, dyspnea)

Compression of adjacent structures : trachea, esophagus, Superior vena cava, recurrent nerve palsy, Horners syndrome

Endocrine syndrome

Hypertension       : pheochromocytoma

Hypercalcemia    : parathyroid tumor

Thyrotoxicosis    : intrathoracic goiter

Gynecomastia     : choriocarcinoma

Systemic consequence : Pel-Ebstein fevers in Hodgkins disease

 

95% of incidental radiographic findings are benign.

In symptomatic patients, 50% are found to be malignancy.

In age <2 years old. 87% of benign present with tracheal obstruction.

Poorer prognosis is associated with Horners syndrome, vocal cord paralysis, hemiplegia.

 

Diagnosis

Chest X-ray : localizing lesion.

CT (+ oral or IV Contrast) :

It is most diagnostic of benign pathology.

Appearance of solid malignancies is less definitive.

Malignant characteristics are readily demonstrated.

MRI

It has benefits for vascular lesions, Heart and Great vessels

Contraindications :

  • pacemakers or cerebrovascular metal clips
  • Critically ill on monitors

Barium Swallow : for invasion, compression and displacement of esophagus.

Arteriography : is the diagnostic standard for pre-operative evaluation of major vascular disorders.

Venous Angiography : reveals extent of involvement and nature of collateral channels in SVC obstruction.

Myelography : is for posterior mediastinal tumors (replaced by CT+MRI).

Radioisotope : is to visualize the anterior mediastinal mass.

Endoscope : is for esophagus and tracheobronchial tree with biopsy

Percutaneous transbronchial or transesophageal needle biopsy

Mediastinoscopy and parasternal Mediastinotomy : for lymphoma or thymoma

Definitive Resection :

  • small
  • anatomically discreet
  • encapsulated mass

 

 

Neurogenic Tumor

 

It arises from sympathetic ganglion or intercostal nerves.

It is most commonly found in posterior mediastinum.

Incidence : Adulthood, 10-20% are malignant.

Higher proportion of childhood are malignant.

Pain, caused by nerve compression or bony erosion, is the most common symptom.

Hemiparesthesis, hemiparesis, cord compression can be found : Dumbbell extension is characteristic in some cases.

Hormonally active tumors cause Hypertension, flushing, diarrhea, diaphoresis, anorexia, fever.

 

Types of neurogenic Tumors

  • Neurilemoma
  • Neurofibroma
  • Neuroblastoma
  • Ganglioneuroma, Ganglioneuroblastoma
  • Paraganglionic Tumors

 

Neurilemoma (Schwannomas)

Schwannoma is the most common tumor neurogenic tumor(40-60%).

It arises from Schwann cells in intercostal nerves.

It is hard, yellowish, well-encapsulated.

Most are benign

Dumbbell extension could be found but not common.

 

Neurofibroma

Neurofibroma arises from nerve sheath and nerve cells

It is 10% of neurogenic tumor.

It is Poorly encapsulated, resemble neurilemomas radiographically.

If it is found with Von Recklinghausens Disease, risk of malignant degeneration is increased.

It has poor prognosis.

 

Neuroblastoma

It is most poorly differentiated neurogenic tumor.

It arises from sympathetic nervous system

10% occur as primary lesion.

Vanillylmandelic acid, an active metabolite, causes Hypertension, fever, vomiting, diarrhea.

Because it is radiosensitive, debluking followed by RTx is the treatment of choice.

It has good prognosis if found in mediastinum 1st year of life.

 

Ganglioneuroma, Ganglioneuroblastoma

Ganglioneuroma

It arises from mature cells in sympathetic ganglia.

It is found in younger age group.

Radiographic : triangular configuration.

Ganglioneuroblastoma

It arises from mixture of mature and immature cells.

It found in the age <3 years old.

 

Paraganglionic Tumors

Pheochromocytomas

It arises from chromaffin paraganglionic tumors.

It can produce catecholamines.

It is 1% of all pheochromocytomas.

It is more silent, more often malignant.

Chemodectomas

It is non-Chromaffin in origin.

It arises from chemoreceptors :

  • aortic arch
  • vagus
  • aorticosympathetics

 

Treatment : Operation :

Operation is performed in most of posterior mediastinal neurogenic tumors

Incision : Posterolateral thoracotomy

CT à intervertebral foramina and vertebral bodies

MRI à intraspinal extension

Intraforaminal extension à combined thoracic and neurosurgical procedure

Malignant

Excised if possible

Neuroblastoma

Radical operations are approached selectively

Active Pheochromocytoma

Pre-operative medical management of paroxysmal Hypertension.

 

 

Thymoma

 

Thymoma is the most common tumor in anterior mediastinal mass.

It is found second most common among tumors and cysts.

Symptoms

  • Mass effects : cough, chest pain, dyspnea, SVC obstruction
  • Systemic effects (Paraneoplastic syndrome) : Myasthenia gravis (most common systemic effect, poorer prognosis), hypogammaglobulinemia, pure red cell aplasia.

There is no characteristic radiographic feature.

Diagnosis is provided by excised mass.

Types :

  • lymphocytic
  • epithelial
  • mixed

Pleural metastases could be found.

Surgery : median sternotomy à 65% curative

 

 

 

 

Lymphoma

 

50% of Hodgkins disease and non-Hodgkin lymphoma are found in mediastinum.

It is the most common mediastinal malignancy.

It is found in anterior mediastinum.

Treatment : chemotherapy and radiotherapy

Resection is never indicated.

Surgery is used only for diagnosis or determining residual active tumor after treatment.

 

 

 

Teratodermoid Tumors

 

It is found in anterior mediastinum.

It is composed of multiple tissue type.

It arises from bronchial cleft and pouch cells and is associated with thymus.

Mediastinum is the second most common location (It is most commonly arise in Gonad)

Symptoms

  • Non-specific mass effect
  • Cough productive of hair and sebum :
    • Pathognomonic but rare

Radiographic

large, well circumscribed anterior mediastinal mass

20-50% are calcified.

CT : fat density in the center of cystic mass

AFP and B-hCG à malignancy

Treatment

Excision through median sternotomy is best for Diagnosis and treatment.

Imcomplete resection is occasionally necessary.

 

 

 

 

Germ-Cell Tumors

 

Germ cell tumors is a rare tumor found in anterior mediastinum.

Histogenesis is poorly understood.

It may arises from pluripotential primordial germ cells.

Teratoma is end point of benign differentiation

Types

  • Seminoma
  • Embryonal cell CA
  • ChorioCA
  • Malignant teratoma
  • Endodermal sunus CA (yolk sac)

Incidence : Young adult, male>female 4x

It is highly malignant.

80-90% are symptomatic.

Symptoms :

Nonspecific, mass effect

Investigations :

Posteroanterior and lateral CXR : 90% detected

CT

Serum tumor markers

hCG  : chorioCA, seminoma, ECC

AFP  : ECC, yolk sac

Metastasis from gonadal tumor must be excluded by ruling out the retroperitoneal involvement.

Treatment

  • Chemotherapy
  • Surgery for residual mass

 

 

 

 

 

Mesenchymal Tumors

 

Lipoma

It is most common mesenchymal tumor.

It has no fixation.

It is asymptomatic despite of enormous size.

 

Fibroma

More dense and less common than lipoma.

 

Tumors of Vascular origin

  • Hemangiomas
  • Malignant hemangiopericytoma
  • Lymphangioma (cystic hygroma)

Uniform density on CXR and cystic mass on CT.

 

 

Endocrine Tumors

 

Thyroid

It spreads by direct substernal extension.

Treatment : Radionuclide

 

Parathyroid

It is approachable through a cervical incision.

It is associated with upper pole of thymus.

 

 

Mediastinal Cysts

 

Mediastinal cyst is the most common found in middle mediastinal compartment.

Chest X-ray : opaque densities in typical location

CT : near water density in characteristic location

 

Pericardial Cysts

Pericardial cyst is the most common mesenchymal cyst.

It is always asymptomatic.

                   It is most commonly found at right cardiophrenic angle, occasionally communicate with pericardium.

Treatment : close observation

 

Bronchogenic Cysts

It is located just posterior to carina or main stem bronchi.

Air-fluid level found in tracheobronchial tree distinguish bronchogenic cyst from pericardial cyst.

Viscid fluid is found in the cyst.

Contrast esophagogram is helpful for diagnosis.

It is lined by ciliated respiratory epithelium.

Surgery : posterolateral thoracotomy

 

Enteric Cyst

It is found in posterior mediastinum adjacent to esophagus.

Its rarely found to be communicated with esophagus.

Its lined by intestinal mucosa, containing clear colorless mucoid fluid.

Peptic ulcer is found if its lined by aberrant gastric mucosa.

60% in Patients age <1 years old have symptoms of tracheal and esophageal compression.

Chest X-ray, esophagogram, CT with contrast are helpful.

Surgery : posterolateral thoracotomy

 

Summarized By Thirayost Nimmanon

ػ ʶ ҹ

  

Ѻاش 15/06/2010

FollowHisSteps.com

ѺʹѺʹع Web Hosting ҡ SPAComputer.com, ThaWang.com