Posterior Mediastinal LesionsAlireza Kashani

Mediastinal Compartments Posterior Mediastinum:

Also called paravertebral compartment

Defined by : Posterior Pericardium Anterior Spinal Ligament Superiorly: T4 vertebral

body Inferiorly: Diaphragm

Contains: Oesophagus, Descending

Aorta, Sympathetic Chain, Vagus Nerves, Thoracic Duct, Azygos and Hemiazygos veins, and Lymph Nodes

Epidemiology Adults:

65% anterosuperior 10% middle 25% posterior compartments

Children: 25% anterosuperior 10% middle 65% in posterior compartments

Generally the incidence of posterior mediastinal lesions is higher in children.

50% are asymptomatic and are diagnosed incidentally

The absence of symptoms is generally is a clue to a benign lesion

Symptomatic lesions: Children: 60%-80% Adults: 50%-60%

Diagnosis CT Scan is the diagnostic modality of choice and is superior to

even MRI in majority of the cases

MRI rarely indicated

Thoracic US is not helpful in posterior mediastinal lesions

Biopsy: is not necessary in majority of the cases and likelihood of a positive result parallels the presence of symptoms If needed:

CT-guided Thoracoscopic Limited posterolateral thoracotomy

Neurogenic Tumours Young adults and children

They are the most common malignant neoplasm in children but they are less common than anterior mediastinal malignancies in adults. Lymphomas and Thymomas are more common in adults

Malignancy rate: Children: 50% Adults: 10%

They originate from embryonic neural crest cells around the spinal ganglia and from either sympathetic or parasympathetic components

Neurogenic Tumours Source:

Intercostal nerve: Neurofibroma : benign

Of patients with nerve sheath tumours 25%-40% have multiple neurofibromatosis (von Recklingausen’s disease) and the incidence of malignancy is more common in these patient

Neurilemoma (Schwannoma) : Mostly benign but malignant schwannomas are rare The most common neurogenic tumor

Neurogenic Sarcoma (rare) Sympathetic Ganglia: can also have pheochromocytoma

Ganglioneuroma Ganglioneuroblastoma Neuroblastoma

Other: phrenic nerves, Vagus nerves

Neurogenic Tumours Those with benign lesions are generally asymptomatic

Malignant tumors might present with symptoms such as: Spinal cord compression Cough Dyspnea Chest wall pain Hoarseness Rarely Horner’s syndrome

Rarely pheochromocytoma: Neuroblastoma or ganglioneuroma In all symptomatic patients, esp. those with significant hypertension it is

necessary to check for 24 h urine HVA (homovanillic acid) and VMA (vanillylmandelic acid)

If elevated then prior to operation to avoid adrenergic crisis: α-adrenergic blockers beta-blockers

Neurogenic Tumours Intercostal nerves:

Neurofibroma Poorly encapsulated Random arrangement of spindle-shaped cells

Neurilemomas The most common neurogenic tumor Well-encapsulated Firm, gray-tan Two morphologic types:

Antoni’s type A: Organized architecture with a cellular palisading pattern of

growth Antoni’s type B:

Loose reticular pattern

Both of the above can happen as parts of neurofibromatosis type 1 (von Recklinghausen’s disease) and if left untreated can degenerate to neurosarcoma

Neurofibroma

Neurilemmoma – Mixed A and B

Neurilemmoma – Antoni A

Neurilemmoma – Antoni B

Sympathetic Source

Sympathetic Source Neuroblastic Tumors:

Arising from primitive sympathetic ganglia

Comprise: Neuroblastoma Ganglioneuroblastoma Ganglioneuroma

These differ in their degree of cellular and extracellular maturation Immature tumors:

Tend to be aggressive Occur in younger patients

(median age < 2) Mature tumors:

Older children (median age 7)

More benign Anywhere sympathetic nervous

tissue exists: Neck Posterior Mediastinum Adrenal Gland Retroperitoneum Pelvis

Sympathetic Source Ganglioneuroma:

The most common neurogenic tumor occurring in children Benign Composed of gangliocytes and mature stroma Early age Located in the paravertebral region

Ganglioneuroblastoma: Composed of mature gangliocytes and immature neuroblasts Intermediate malignant potential

Ganglioneuroma

Ganglioneuroma

Sympathetic Source Neuroblastoma:

Children < 4 y Small, round immature cells organized in rosette pattern Highly invasive Metastasized by the time the diagnosis is made:

Regional lymph nodes, bone, brain, liver, lung Some may have benign course Symptoms:

Cough, dysphagia, chest pain, and occasionally paraplegia Paraneoplastic:

Profuse watery diarrhea due to VIP Opsoclonus-Polymyoclonus syndrome Pheochromocytoma-like syndrome

Prognosis: Influenced by: DNA content, tumor proto-oncogenes, and catecholamine

synthesis The above aid in categorizing patients with neuroblastoma into low,

intermediate, and high-risk Rx: Resection +/- Chemotherapy

Neuroblastoma

Neuroblastoma

Investigations CT:

Can help to identify the tumor and extent of involvement Those from peripheral nerves:

Well-defined, round or oval masses Noncalcified

Neurilemoma: Variable enhancement: homogenous or heterogenous On enhanced CT: variable attenuation

Neurofibroma: Usually homogenous Low-attenuation On enhanced CT: homogenous enhancement or with early central

blush Malignant nerve sheath tumors show variable attenuation

Investigations CT:

Sympathetic Chain Tumors: Expand along the spinal axis No calcification or bone changes

Ganglioneuroma: Oblong homogenous low-attenuation lesions on both enhanced and

unenhanced CT Neuroblastoma:

Aggressive soft tissue lesions with calcification Ganglioneuroblastoma:

Mixed features of above Paragangliomas:

Appear in aortopulmonary window High contrast enhancement

Investigations MRI: for dumbbell tumors

FNA

Tumor Markers: S-100

Dumbbell Tumors Tumors of the posterior

mediastinum that extend into the spinal canal via the intervertebral foramen

It is necessary to identify these tumors to have a better planning, as inaccurate diagnosis would lead to intra-spinal hemorrhage and cord compression

MRI can identify these Smoothly rounded, homogenous

density abutting the vertebral column

Rarely present with cord

compression symptoms

They comprise 10% of patients with neurogenic tumors

Only 1-2% are malignant

Management Standard of Care:

Surgical resection via thoracotomy or thoracoscopy Most of the neurogenic tumors can be resected via thoracoscopy; however,

malignant transformation, local invasion, and tumors larger than 5 cm increase the likelihood of conversion to thoracotomy

In most cases the tumor can easily be mobilized via thoracoscopy but any difficulty necessitates the conversion to thoracotomy

Resection of the nerve root is necessary in most of the cases A widened intervertebral foramen might be indicative of invasion of vertebral

canal (dumbbell tumor) and in these cases it is necessary to involve a neurosurgeon to assist in full resection of the tumor via a laminectomy in one stage procedure

Neuroblastoma: Spontaneous regression has been reported Stage:

I (noninvasive): Surgical resection alone II (locally invasive on same side of midline): Surgery + RTx III (invasive across the midline): Debulking + RTx + ChemoTx + Second-

look operation Children < 1 : good prognosis, prognosis has inverse correlation with age

Oesophageal Masses These include:

Neoplasm Cysts Diverticula Hiatal Hernia Mega-oesophagus Oesophageal Varices

Cysts Rare, benign, congenital

20% of all mediastinal lesions

Include: Bronchogenic Hydatid Enteric Intramural Oesophageal Neuroenteric Cysts

CT is the most effective modality of diagnosis

Bronchogenic 60% of all mediastinal cysts

Location: Lung parenchyma Mediastinum

Histology: Ciliated columnar epithelium Cyst wall: cartilage, mucus

glands, smooth muscle Rarely communicate with the

tracheobronchial tree

Symptoms: Occasional compression on the

adjacent structures Recurrent infection Pain, Cough, Hemoptysis

Rx: If incidental finding in an

otherwise asymptomatic patient: observation is accepted

If symptomatic esp. if pain, cough, or hemoptysis the resection is strongly advised.

Bronchogenic

Bronchogenic

Bronchogenic Dysphagia: as a result of

compression effect on the oesophagus

Presence of air-fluid level: suggests the possibility of communication with the tracheo-bronchial tree and increased chance of recurrent infections; hence, the possible need for resection

If it becomes infected, it is very likely that eradication is unsuccessful and it needs to be resected

Symptoms tend to develop with

time and hence the resection is advised in a healthy state before becoming symptomatic.

They can be resected via thoracoscopy or if in superior mediastinum via mediastinoscope.

Bronchogenic

Bronchogenic

Gastroenteric Cysts Gastroenteric or duplication cysts:

peri-oesophageal lesions that arise from posterior division of the primitive foregut.

Features: Posterior or middle mediastinal mass Within or adjacent to the oesophageal

wall Communication with UGIT is

uncommon

Histology: Nonkeratinizing squamous, ciliated

columnar, gastric, or small intestinal epithelium

Epithelium is not a good differentiating feature from bronchogenic cysts: Presence of two muscular layers in

oesophageal cysts Cartilage and bronchial glands in

bronchogenic cysts

Usually asymptomatic, but symptoms: Resp: Cough, SOB, Recurrent

Pulmonary Infections, Chest Pain If gastric mucosa: perforation into the

oesophagus can cause haematemesis, or erosion into the adjacent lung can cause an abscess

Dx: EUS, Chest CT, Technetium Tc 99m (to identify gastric mucosa)

Rx: Resection: symptomatic, unclear cysts

– whether cystic or solid Observation: clearly cystic lesions,

otherwise asymptomatic

Gastroenteric Cysts

Gastroenteric Cysts

Neuroenteric Cysts 5-10% of foregut lesions

Infants younger than 1

Connection to the meninges usually through a stalk

Associated with the congenital defects of the spine

Endodermal and ectodermal or neurogenic elements Failure of separation of the notochord from the primitive gut

CT evidence of mediastinal lesion with either of : Scoliosis, Hemivertebrae, Spina Bifida should prompt the possible Dx of neuroenteric cysts.

Other Primary or metastatic lesions of

thoracic spine

Lymphomas : esp. Hodgekins

Infections such as TB

Post-traumatic haematoma

Descending thoracic aneurysm

Extramedullary hematopoiesis

Castleman’s Disease

Angiomyolipoma

Extralobar Pulmonary Sequestration

Neuroendocrine Carcinoma

Mediastinal Ependymoma

Cellular Hemangiomas

Melanotic Paraganglioma

Pancreatic Pseudocyst Mediastinal Extension

Castleman’s Disease Giant lymph node hyperplasia

Vascular tumors surrounded by large LAP

Types : Localized: Hyaline Vascular,

Plasma Cell Generalized or Multicenteric

Hyaline Vascular: 90% of lesions Incidental finding in otherwise

asymptomatic Spinal cord compression has

also been reported Rx: Surgical excision, RTx is

ineffective

Plasma Cell:

More symptomatic: fever, fatigue, weight loss, hemolytic anemia, high ESR and hyper-γ- globulinemia as the result of the over production of IL-6

Resection is Rx of choice

Generalized: Histologic features of both of the

localized forms Older patients Symptoms:

Severe systemic symptoms Generalized LAP Hepatosplenomegaly

Mortality : 50% with median survival of 27 months and Progression to lymphoma

Castleman’s Disease - Hyaline

Castleman’s Disease - Plasma