Mediastinal Masses

MEDIASTINAL MASSES

BY: joseph soqueña, MD

MEDIASTINAL MASSESStatistically > 60%

ThymomasNeurogenic TumorsBenign CystsLymphadenopathy (LAD)

Children Neurogenic tumors Germ cell tumors Foregut cysts

MEDIASTINAL MASSES

In adults the most common are: Lymphomas LAD Thymomas

Thyroid masses

MEDIASTINAL MASSES

Localizing: mediastinal mass will not contain air

bronchograms.

The margins with the lung will be obtuse.

Mediastinal lines (azygoesophageal recess, anterior and posterior junction lines) will be disrupted.

MEDIASTINAL MASSESLocalizing:

There can be associated spinal, costal or sternal abnormalities.

A lung mass abutts the mediastinal surface and creates acute angles

with the lung, while a mediastinal mass will sit under the surface creating obtuse angles with the lung

MEDIASTINAL MASSES

LEFT: A lung mass abutts the mediastinal surface and creates acute angles with the lung.RIGHT: A mediastinal mass will sit under the surface of the mediastinum, creating obtuse angles with the lung.

MEDIASTINAL MASSES

A. Pancoast tumor. B. Thymoma

ANATOMY

ANATOMY

Anatomic divisions:1. anterior (prevascular)2. middle (cardiovascular)3. posterior (postvascular)

Anterior compartmentBoundaries:

Ant – sternumPost – pericardium, aorta, &

brachiocephalic vessels merges superiorly with the

anterior aspect of the thoracic inlet and extends down to the level of the diaphragm

Anterior compartmentContents

thymus, lymph nodes, ascending aorta, pulmonary artery, phrenic nerves and thyroid.

Masses: most common will be of thymic

or lymphnode in origin.

Anterior compartment

The four T's make up the mnemonic for anterior mediastinal masses::

1. Thymus2. Teratoma (germ cell)3. Thyroid4. Terrible Lymphoma

Anterior compartment:Appearance on conventional

radiograph: displaced anterior junction line obliterated cardiophrenic angles obliterated retrosternal space hilum overlay sign effacement/ dense ascending aorta


WIDENING OF THE SUPERIOR MEDIASTINUM AND OBLITERATED RETROSTERNAL SPACE


Hilum Overlay Sign: hilar vessels are seen through a mediastinal mass

Anterior compartmentThymoma

most common primary neoplasm to occur in the anterior mediastinum

arise from thymic epithelial cells

affects man and women equally

uncommon in children and is diagnosed between ages 40 - 60

may have cystic component and sometimes comprise most of the tumor


noninvasive (encapsulated) and invasive symptoms are cause by pressure of the

enlarged thymus on the trachea and blood vessels

associated conditions:a. pure red cell aplasiab. myasthenia gravis (most common

paraneoplastic disease asso.)

c. hypogammaglobulinemia


Thymoma in a 55-year-old woman with recurrent lung cancer. A homogenous mass with convex margin is demonstrated within the thymus. Left lung nodule (white arrow) represents lung cancer recurrence.

http://www.ncbi.nlm.nih.gov/core/lw/2.0/html/tileshop_pmc/tileshop_pmc_inline.html?title=%20%5BObject%20name%20is%20ci05013908.jpg%5D&p=PMC3&id=1665238_ci05013908.jpg

Anterior compartment Thymoma

Invasive thymoma. Homogeneous, anterior mediastinal mass extends to the left. Irregular interface suggests extracapsular invasion; lung and pericardial invasion were found at surgery.



Invasive thymomas. (A) Irregular interface with lung (arrow) suggests pulmonary invasion (surgically proven). (B) Encasement of the aorta and mass protruding into the lung, suggesting invasion.



Thymoma tends to spread along the pleural surfaces and may extend into the abdomen via the retrocrural space. (A) Small discrete pleural implant (black arrow), visualized to advantage on lung window. (B) Left retrocrural spread (white arrow). (C) Retroperitoneal implant (black short arrow).



A small thymoma anterior to the heart (marked with the red line)

http://upload.wikimedia.org/wikipedia/commons/3/3f/Tumor_Thymoma1.JPG


WHO Histologic classification: A - a tumor composed of a population of neoplastic

thymic epithelial cells having a spindle/oval shape, lacking nuclear atypia and accompanied by few or no non-neoplastic lymphocytes

AB - tumor in which foci having the features of type A thymoma are admixed with foci rich in nonneoplastic lymphocytes

B1 - tumor resembles the normal functional thymus because it contains large numbers of cells that have an appearance almost indistinguishable from normal thymic cortex with areas resembling thymic medulla


WHO Histologic classification:B2 - the neoplastic epithelial component of this

tumor type appears as scattered plump cells with vesicular nuclei and distinct nucleoli among a heavy population of nonneoplastic lymphocytes

B3 - is predominantly composed of epithelial cells that have a round or polygonal shape and that exhibit no or mild atypia. The epithelial cells are admixed with a minor component lymphocytes.

C - a thymic tumor exhibiting clear-cut cytologic atypia and a set of cytoarchitectural features no longer specific to the thymus, but rather analogous to those seen in crcinomas of other organs


Pathologic characteristics: most type A & B are well encapsulated and round or slightly lobulated

usually 5 to 15 cm in diameter

subdivided into numerous lobules by variably thick fibrous band

some may have cystic component


An encapsulated cystic thymoma.

http://upload.wikimedia.org/wikipedia/commons/0/07/Encapsulated_cystic_thymoma.jpg


MEDIASTINUM: LOCALLY INVASIVE, CIRCUMSCRIBED THYMOMA (MIXED LYMPHOCYTIC AND EPITHELIAL AND MIXED POLYGONAL AND SPINDLE)

http://upload.wikimedia.org/wikipedia/commons/6/60/Locally_invasive_circumscribed_thymoma.jpg


Radiologic Manifestations: most type A & B are situated near the jxn of the heart and great vessels radiographically, they are round or oval, and their margins are usually smooth or lobulated displace the heart and great vessels posteriorly on CT, they are typically located in the region of the thymus anterior to the aortic root and main pulmonary artery & project to one side of the mediastinum

Anterior compartmentThymic Carcinoma (type c)

5 – 15cm in diameter

are often found to invade adjacent tissues at the time of diagnosis

most will show evidence of extension outside the thymus with focal or diffuse

obliteration of the adjacent fat planes.

squamous cell CA- most common histologic type


Radiologic presentation large ant mediastinal mass with irregular or poorly defined margins.

CT scan presentation: can have a homogenous ST attenuation or heterogenous due to necrosis or hemorrhage calcification is present in 10% of cases Pericardial or pleural involvement and

pleural effusion are frequent findings

.


Other findings: hilar lymph node enlargement

diaphragmatic elevation suggesting phrenic nerve palsy

lung nodules suggestive of metastases


Thymic SSC. Large heterogenous mass extending along the pericardium, with probable invasion (arrows). Six weeks following a Chamberlain procedure (left anterior thoracotomy) there is new chest wall invasion, compatible with tumor seeding in the surgical wound.



High grade thymic carcinoma with mediastinal lymph node enlargement (black arrow) and pleural involvement, including pleural mass (white arrow head) and loculated pleural effusion (white arrow).



Thymoma. Large mass extending into the right hemithorax, containing punctuate and coarse calcifications. Low attenuation regions suggesting necrosis and/or hemorrhage

Anterior compartmentThymic Lymphoma

2nd most common primary anterior mediastinal mass.

cancer of the lymphatic system

indistinguishable from other solid neoplasm arising w/in the thymus

most commonly involves the anterior mediastinal and hilar nodal group

enlarged spleen displacing the gastric bubble medially in the upper abd.

Portion of the frontal chest film


CT advantages to better characterized and

localized for staging, prognosis and

therapy guidance for trans thoracic or

open biopsy to monitor response to therapy detection of relapse


A, B) Thymic lymphoma. Thymic mass and enlarged mediastinal and right hilar lymph nodes.


Anterior compartmentThymic hyperplasia:

meas: CT thickness = <20 yrs – 1.8cm

>20 yrs – 1.3cm

rare in adults inc in size with normal gross architecture histologic appearance. rebound to atrophy 2nd to chemotherapy or by hypercorticolism

Anterior compartmentCT images of the normal involution of the thymus

A. childhood B. early adulthood C. middle age D. late adulthood


Anterior compartmentThymic hyperplasia:

Thymic hyperplasia in a 29-year-old female. A. Mild diffuse thymic enlargement with biconvex margins. B. CT scan 3 years later demonstrates residual normal thymic tissue.


Anterior compartmentGERM CELL TUMORS

1. TERATOMA most common GCT

consist of one or more types of tissue, usually derived from more than one germ layer

majority are cystic and benign

if solid most likely malignant


TERATOMA subdivided into

a. mature – most common form - 8 to 10cm in diameter, often

multicystic- ectodermal elements (epidermis &

skin)b. immature

- same as mature but contain a foci of primitive less well organized tissue resembling seen in fetus

c. teratoma with malignant transformation

- mature tiss + immature tiss and neoplastic tisssue


TERATOMASymptoms:

shortness of breath cough sensation of pressure or pain in

the retrosternal area malignant forms may obstruct the

SVC mediastinitis, empyema, fistula

formation, due to rupture of cystic form


TERATOMARad features:

localized mass in the anterior compartment close to the origin of the great vessels in the heart

calcification is present in 20%

on CT mature teratoma can have smooth or lobulated margins and may contain one or more cystic areas


TERATOMAComplication:

atelectasis and obstructive pneumonitis (airway compression)

pneumonitis (rupture into the lung)

effusion (rupture into the pleural space or pericardium)


2. SEMINOMA second most common mediastinal

germ cell tumor

majority are solid, but can have multilocular cystic

component

occurs almost exclusively in men

average age of occurrence is 20-30 y/o


SEMINOMARadiographic appearance:

invasion of adjacent structures is uncommon

large masses that project to one or both sides of the mediastinum

homogenous attenuation on CT & only enhances slightly with contrast

Contrast-enhanced axial CT scan shows an ill-defined anterior mediastinal mass with irregular borders that is infiltrating the mediastinal fat. CT-guided needle biopsy revealed a mediastinal seminoma.


THYROID TUMORS Multinodular Goiter

- most frequent thyroid tumor- commonly in women in their forties

80% of the tumors arise from a lower pole or the isthmus & extends into the ant or mid mediastinum 20% arise from the post. aspect of thyroid and extend to the post aspect of the mediastinum

Anterior compartmentTHYROID TUMORS

Radiographic appearance: sharply defined, smooth or lobulated

mass that causes displacement and narrowing of the trachea

ant & mid mediastinal mass, displaces the trachea post & lat

post mediastinal mass pushes the trachea ant

the thyroid enhance intensely on CT w/ contrast

focal non enhancing areas of low attenuation as a result of hemorrhage or cyst

Anterior compartmentLIPOMA:

CT scan is usually diagnostic has lower attenuattion than most mediastinal masses does not cause symptoms may have an hourglass appearance, with homogenous fat attenuation surgical excision is curative

Anterior compartmentLIPOMATOSIS:

non-neoplastic

excessive accumulation of fat asso with hypercortisolism,(Cushing’s synd, ectopic adrenocorticotrophic hormone syndrome, long term corticosteroid therapy)

Rad features - smooth, symmetrical widening of the mediastinum - widening usually extends from the thoracic inlet to the hila bilaterally - CT is diagnostic

Anterior compartmentDEVELOPMENTAL ANOMALIES:

1. HEMANGIOMA

can isolated or part of a multifocal hemangiomatous malformation

most are located in the upper portion of the anterior mediastinum

2. Lymphangioma Types

a. cystic hygroma – extends from the neck into the mediastinum, usually occurs in infants


Lympangiomab. found in adults and located in the lower

anterior mediastinum

sharply defined, smoothly marginated mediastinal mass that displaces adjacent midiastinal structures

on CT – smoothly marginated cystic mass with homogenous water density,

that can either displace or surround adjacent vessels


3. Mesothelial (pericarial) cyst congenital and result from aberrations in formation of the coelomic cavities.

common in the vicinity of the heart

spherical or oval, thin walled, and often translucent

most are unilocular

Anterior compartmentDEVELOPMENTAL ANOMALIES

Messothelial (pericarial) cystRad findings:

located in the cardiophrenic angles, most commonly in the right

smooth, round and oval 3 – 8 cm in diameter CT – has a water density, smooth,

round, or oval cystic lesion abutting the pericardium

Middle compartment

Contents:1.pericardium and its contents2.aortic arch & proximal great arteries3.central pulmonary arteries & veins4.trachea and main bronchi5 lymph nodes6. hila (considered as extension)

Middle compartmentPresentation on conventional

radiograph1. widened paratracheal stripes.2. AP window mass3. displaced azygoesophageal recess in the right4. mass on posterior trachea5. lateral “doughnut”

Middle compartment

AP chest radiograph showing widening of the azygoesophageal recess on the right. There is an apparent widening of the paravertebral line on the left. On the lateral film the mass is anterior to the spine and therefore is located in the middle mediastinal.

Middle compartment

CT showing the azygoesophageal recess is displaced to the right due to oesophageal varices (blue arrow) and there is also a new interface on the left. This is a patient with cirrhosis of the liver and varices as a result of portal hypertension.

Middle compartment

PA film showing a lobulated paratracheal stripe on the right.On the lateral radiograph there is a density overlying the ascending aorta and filling the retrosternal space.These findings indicate a mass in the anterior aswell as in the middle mediastinum.

Middle compartment

A lobulated mass surrounding the right bronchus creating a 'doughnut' with the bronchus as the hole in the doughnut.

Middle compartmentMasses1. Lymph node enlargement

most middle mediastinal lymph node masses are malignant

malignant causes:- bronchogenic CA- extra thoracic malignancy- leukemia- lymphoma

Middle compartmentLymph node enlargement

benign- sarcoidosis- mycobacterial and fungal- angiofolicular lymph node

hyperplasia (Castleman disease)

- angioimmunoblastic lymphadenopathy

8 (grey) = para-oesophageal9 (brown) = pulmonary ligament nodes10R and 10L (yellow) = right and left hilar11R and 11L (green) = right and left interlobar 12R and 12L (pink) = right and left lobar nodes13R and 13L (pink) = right and left segmental 14R and 14L (pink) = right and left subsegmental Ao = aortic arch, PA = main pulmonary artery,,

1 (red) = highest mediastinal nodes,

2R and 2L (dark blue) = right and left upper paratracheal nodes

3 (pink) = pre-vascular and retrotracheal nodes

4R and 4L (orange) = right and left lower paratracheal

5 (black) = subaortic nodes

6 (red) = para-aortic nodes.

7 (blue) = subcarinal nodes

Middle compartmentLymph node enlargement

Rad appearance: multiple bilateral mediastinal

masses that distorts the lung/mediastinal interface.

round or oval soft tissue masses > 1cm in their short axis diameter

if solitary, tends to be elongated and lobulated rather spherical

calcifications can sometimes be seen

Middle compartment

Lymph node enlargement Rad appearance:

CT scan is more sensitive in detecting nodal calcification

CT is unable to distinguish between benign inflamatory nodes and those involved by malignancy.

Middle compartmentMesothelial cysts:1. Congenital Bronchogenic Cyst

result from anomalous budding of the tracheobronchial tree.

walls should be lined with respiratory epithelium

arise w/in the mediastinum in the vicinity of the tracheal carina

Middle compartmentCongenital Bronchogenic Cyst

frequently seen in the subcarinal or right paratracheal space

sometimes maybe seen in hilum, posterior mediastinum, periesophageal region

single smooth, round or elliptic mass

CT is the method of choice for diagnosis

Middle compartment

Congenital Bronchogenic Cyst Benign – well defined thin walled

mass of fluid density that fails to enhance with contrast.

- some are lobulated

Middle compartment

(Mesothelial) Pericardial Cyst: arise from the parietal pericardium

most are 3-8cm in diameter

commonly in the anterior cardiophrenic angles

more common in the right than in the left

usually present as a unilocullar cystic mass on CT scan

Posterior compartmentContents

descending aorta azygous and hemiazygous vein thoracic duct intercostal and autonomic nerves

Conventional radiographs Cervicothoracic Sign Widening of the paravertebral stripes

Posterior compartment

• Cervicothoracic sign - the anterior mediastinum stops at the level of the superior clavicle.Therefore, when a mass extends above the superior clavicle, it is located either in the neck or in the posterior mediastinum.When lung tissue comes between the mass and the neck, the mass is probably in the posterior mediastinum.

Posterior compartment

There is widening of the paravertebral stripes on both the left and the right on the this PA radiograph.On the lateral radiograph there is a severely narrowed disc space.

Posterior compartment most are neurogenic in nature

- from the sympathetic ganglia (eg neuroblastoma)

- from the nerve roots (eg schwannoma or

neurofibroma). lymphadenopathy neuroenteric cysts, schwannomas or meningoceles.

Posterior compartment1. Neurogenic Tumors.

Classification:a. neurofibroma, schwanoma

(arising from the intercostal nerves)

b. ganglioneuroma, ganglioneuroblastoma, neuroblastoma (sympathetic ganlia)

c. chemodectoma, pheochromocytoma (paraganlionic cells) neuroblastoma & ganlioneuroma – common in children neurofibroma & schwanoma – affects adult more frequently

Posterior compartmentNeurogenic Tumors.

Rad appearance: intercostal nerve tumors appear

as round or oval paravertebral soft tis masses

CT – smooth or lobulated paraspinal soft tissue mass w/c may erode adjacent vertebra or rib

Posterior compartmentEnteric/Neuroenteric cyst

fluid filled masses lined by enteric epithelium

esophageal cyst – arise intramurarly or immediately adjacent to

the esop.

neuroenteric cyst – persistent communication with the spinal canal and asso with congenital defects of the T-spine.

Fluid containing masses

Thymoma Teratoma Pericardial Cyst Foregut Duplication Meningocoele Neuroenteric Cyst Cystic Lymphadenopathy Lymphangioma

Fat containing masses

Thymolipoma

Teratoma (Germ cell tumors)

Esophageal lipoma

Fat deposition

Lipoma

Lipoblastoma

Liposarcoma

Extramedullary hematopoiesis

Enhancing masses

Hyperenhancing lymph nodes

Thyroid tissue

Paragangliomas

Hemangiomas

Vascular Etiologies

THANK YOU

MEDIASTINAL MASSES

ANATOMY

• anterior mediastinum (1) • middle mediastinum (2) • posterior mediastinum (3)


ANATOMYSuperior Med.

bounded by:

sup thoracic aperture (thoracic inlet) inf line from sternal angle ant manubrium post 1st 4

thoracic vert.


http://upload.wikimedia.org/wikipedia/commons/a/ab/Mediastinum.png

ANATOMY1.Anterior

ant body of sternumpost fibrous pericardium

contents: thymus branches of the internal mammary

artery and vein lymphnode inferior sternopericardial ligament fats


ANATOMY2. Middle between the anterior and

posterior subdivision of the mediastinumcontents:

the pericardium and its contents ascending & transverse portion

of the aorta sup & inf vena cava bifurcation of the trachea and

two bronchi pulm artery and veins phrenic nerves and the lymphatic

glands


ANATOMY3. Posterior

ant. By the pericardium, laterally by the mediastinal pleura and posteriorly by thoracic vertebrae

Contents: descending thoracic aortaesophagus thoracic duct, azygos,

7hemiazygos veins autonomic nerves, fats

&lymohnodes


Mediastinal Masses

ANATOMYSuperior mediastinum:

content: aortic arch, brachiocephalic arter,

left common carotid and the left subclavian.

innominate veins, and left and right brachiocephalic veins

vagus nerve, cardiac nerve, phrenic nerve, & left recurrent laryngeal nerve

trachea, esophagus, thoracic duct, thymus and some lymph glands

ANATOMY

MEDIASTINAL DIVISION1. Superior mediastinum

2. Inferior mediastinuma. anteriorb. middlec. posterior

ANATOMY

http://upload.wikimedia.org/wikipedia/commons/a/ab/Mediastinum.png

ANATOMYInferior mediastinum contents:

Ant

http://upload.wikimedia.org/wikipedia/commons/5/5f/Gray967.png

Mediastinal Masses

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