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Normal Thymus

Lt is larger; max at puberty (50g)involutes after puberty; "thymic sail" sign rt lobe; "wave" sign lt lobe from scalloping by ant ribs; infants CT HU~ muscle 26 HU av + 20-30 post CM; >25y fatty

Pericardial recesses

superior, pulmonic, retroaortic, preaortic


oval AP>trans at thoracic inlet; at the manubrium rounded just above the carina shows a horizontal oval ;horseshoe-shaped;

Tracheal Bronchus

only right is known; Displaced (usually apical segm) or supernumarary ( tracheal lobe)

Accessory cardiac bronchus.

from the medial wall of the RBI just below the takeoff of the RULB

DD of mediastinal mass based on

location ( ant/mid/post); nature ( solitary/multifocal/diffuse); Attenuation ( fat/fluid/soft tissue/ca++/post CM)

Anterior M anatomic

sternum-pericardium; fat, ly,

Middle M anatomic

between ant and post mediastinum

Posterior M anatomic

heart-spine; DA; Az; Sup intercostal vein; Thoracic D; Esoph; Vagus

Superior M anatomic

above pericardium, below root of neck; trachea; esoph; thymus; gr vessels

Anterior M Xray

sternum-ant tracheal wall/post border of the heart; thymus/heart/asc aorta/ant portion MPA/pericardium/fat/lymph; ant junction line/cardiophrenic angles/retrosternal stripe/retrosternal space

Middle M Xray

between Ant and Post; trachea/bronchi/SVC/ mid AArch/Azygous/ lymph/Esophagus/Desc Aorta/; Rt and Lt paratracheal stripes/ SVC interface/AP window/Lt subclavian art interface/Azygoesophageal recess/preaortic interface

Posterior M Xray

post to line 1 cm behind the ant margin of the vertebral coumn-chest wall; vertebral bodies/paravertebral tissues/desc aorta/ post azygous vein, hemiazygous vein/ lymph nodes/ paravertebral stripes

Anterior M CT prevascular space

Thymic - hyperplasia/thymoma/thymic CA/ thymic carcinoid/ thymic cyst/thymolipoma/thymic lymphoma and metast
Germ cell tu - teratoma/ seminoma/ Non-seminomatous germ cell tu
Thyroid - goiter, neoplasm
Parathyroid tu or hyperplasia
Lymph nodes - Hodgkins Ly
Vascular malformations
Mesenchymal - lipoma, lipomatosis
Foregut cyst
hemangioma, lymphangioma

Anterior M CT cardiophrenic angle

Lymph nodes - Ly, mets
Pericardial cyst
Morgagni Hernia
Thymic masses
Germ cell tu

Middle M CT pretracheal space

Lymph nodes - Lung ca, sarcoidosis, Ly, Mets, Inf ( tb)
Foregut cyst
Tracheal Tu
Mesenchymal - lipoma, lipomatosis
Thyroid abnorm
Vascular malformations
hemangioma, lymphangioma

Middle M CT AP Window

Lymph nodes - Lung ca, sarcoidosis, Ly, Mets, Inf ( tb)
Mesenchymal - lipoma, lipomatosis
Vascular malformations
Foregut cyst

Middle M CT subcarinal and asygoesophageal recess

Lymph nodes - Lung ca, sarcoidosis, Ly, Mets, Inf ( tb)
Foregut cyst
Dilated Azygous Vein
Esophageal Masses

Posterior M CT (paravertebral region)

Neurogenic Tu - nerve sheath/ sympathetic ganglia/paraganglioma
Foregut cyst
Thoracic spine abn
Esoph masses, varices
Mesenchymal - lipoma, lipomatosis
Lymph nodes - Hodgkins Ly, mets
Azygous, hemiazygous dilated
hemangioma, lymphangioma
thymic or germ cell

Thymic hyperplasia

Incr in size, normal appearance; assoc w AI diseases ( grave's) red blood cell aplasia, sarcoidosis

Thymic Rebound

stress thymus decreses(-40%), then increases(150%); 1-9 mo after; ; assoc w recovery from chemo/stress/burns/; lymphoma - DD rebound vs recurrent tu


thymic epithelium; most common thymic; 50-60yo;Myastenia gravis in 30-40%(10-30% MG have thymoma) Invasive in 30% non invasive 70%, not B or M. Mets out of thorax 3-5%; RF: Sharp margin smooth or lobulated; usually projects to one side of M; Retrosternal clear space or CPAs; CTF: Focal or lobulated mass; homogeneous or cystic; may Ca++; difficult to Dx invasion with certainity surgical staging; MR is limited; Tx Resection +Rad or chemo for invasive beyond capsule; 5ys 75-90% non invasive; 50-60% invasive

Thymic ca

thymic epithelium; 50yo; M on histology; common invasion ,dist M 50-60%; MG rare; appearance indistinguishable from thymoma unless mets visible

Thymic Carcinoid

from neural crest (APUD) cells; usually M; mets maybe; 45yo; Cushing 25-40%; MEN I or II in 20%; appearance like thymoma; more aggressive; dense CMEnhancement; 5ys 65%


fat and thymic tissue; rare; B; young; asymptomatic; large droopy mediastinal mass w fat and strands of tissue; no invasion or recurrence

Thymic Cyst

uncommon; congenital(rare) or acquired(Rad Tx, thoracotomy); Water HU +- hemorrhage and fat; DD cystic lesions w thymoma and lymphoma: thin wall, no mass lesion; water density; no enhancement; can be Ca++ wall

Thymic Ly and Mets

Hodgkin: non specific; + ly nodes; Mets: from lungs and breast; non specific; + ly nodes;

Germ cell : Teratoma

all three germinal layers; 95% ant M 5% Post M; (1)mature - well-diff tissues hair skin, cartillage; B; mc germ cell tu; young; asymptomatic unless large (2) cystic (dermoid cyst) only ectoderm layer skin; B (3) immature - fetal tissues; B for children M agressive for adults(4) malignant - poor prognosis; men RF: smooth round or lobulated; one side of M; Retrosternal clear space or CPAs; Ca 20%; mature big CTF: prevascular space 95% post M 5%; combination of fluid(varyable HU) filled cysts(90%); fat(75%); soft and Ca++ (50%); M compresses and enhances in thick capsule

Germ cell : Seminoma

Men, 29yo; 30% germ cell; large lobulated ant M mass; homogeneous; 5ys 50-75%; radiosensitive

Germ cell : NonSeminoumatous

Cell types: Embryonal CA; Endodermal sinus (yolk sac) tu; ChorioCA; mixed types; large lobulated ant M mass; inhomogeneous infiltrative, ; poor prognosis


almost always connected to cervical thyroid; anterior M 75-90%; posterior M in 10-25%; mulitinodular goiter mc, ca, thyroiditis; RF:sup M mass w trachea narrowing and displacement; CTF high HU mass w marked and prolonged enhancement; inhomogeneous and cystic punctate Ca++; difficult to diff goiter from Ca


mc parath adenoma ( in lower glands)

Lymphoma HD

30% from LY; 85% thoracic involvement; variable appearance

Lymphoma NHL

40% thoracic involvement; common in one! node group

Ly: Castleman Ds

Angiofollicular ly node hyperplasia; unknowm etiology; localized or multicentric; dense enhancement of ly nodes on CT!; 90% hyaline vascular type ( children or young/asymptomatic/localized/B) plasma cell type ( 40-50yo/multicentric/ progressive/ systemic illness) steroids, chemo, resection is tried; axillary, abdominal, other maybe involved

Ly: Sarcoidosis

mediastinal ( mc rt paratracheal) and hilar bilateral(95%) symmetrical 1-2-3 pattern typical +- APW; Ca++ can be present on CXR ( ense, stippled, eggshell) om CT 25-50%; rarely necrotic or enhancing maybe; not as large as Ly

Ly: Inf: TB

active; more often in children; hilar and mediastinal; side of disease; rt side predominates; rt paratracheal is most common; if >2cm necrotic center ( 40-60 HU) often in AIDS+Tb; can obliterate M fat with necrotic area - >abscess ( cold abscess)

Ly: Inf: Histoplasmosis

hilar and mediastinal; acute or subacute; paratracheal, subcarinal, hilar; irreg enhancement, rim enh or necrosis mb

Fibrosing Mediastinitis

TB/Histo/Sarcoidosis/AID/Drugs/Retroperitoenal Fibrosis/Idiopathic; Ca++common; Narrows SVC, trachea, LMB, RPA


FAT =-40 - -130 HU; assoc w Cushing, steroid, obesity, idiopathic 50%; RF: symmetrical upper M; smooth homogeneous, low HU; no compression or displacement; sometimes in CPA and paraspinal. DD mediastinitis, hemorhage, tu infiltration, fibrosis

Lipoma LipoSarcoma

mc prevascular space

Hernias with Fat

Morgagni rt CPA; Bochdalek lt post lat

Foregut Duplication Cyst: Bronchogenic Cyst

60% of FDC; wall contains resp epithelium, smooth muscle, mucous gland or cartilage; 50% subcarinal; 20% paratracheal; 10% retrocardiac; round oval smooth margins; wall thin or invisible on CT, may calcify; fluid 0-40 HU;Up to 50% may be soft tissue attenuation on CT! high signal T1MR Compl inf or hemorhage; Tx resection

Foregut Duplication Cyst: Esophageal Duplication Cyst

GIT mucosa lining, connected to E, no cartilage. 60% in lower post M dysphagia /chest pain /asymptomatic.

Foregut Duplication Cyst:Neurenteric cyst

+vertebral abnormality in 50% cases; MR fo rintraspinal involvement

Pericardial cyst

65% Rt CPA 25% Lt CPA; sharp margin, smooth, low HU

Mediastinal pseudocyst

Pancreatic pseudocyst; symptoms

Lymphangioma, cystic Hygroma

rare, present in childhood; neck 75%, axila 20%; capillary, cavernous or cystic ( hygroma)unilocular or multilocular


ant or post M; vascular, B cavernous 75%( capillary, venous); young

Esophageal Ca

CT: thickening wall; narrowing of lumen; loss of periesophageal fat planes; adenopathy

Esophageal Dilatation

tu; stricture ; achalasia

Esophageal Varices

portal pressure up; CT serpingious soft-tissue opacities identing E wall; enhancing post CM

Hiatal Hernia


Mediastinal abscess


Neurogenic Tu: Peripheral nerve sheath

Shwannoma (neurilemmoma), neurofibroma, neurogenic sarcoma; adults; round, elliptical or lobulated paravertebral mass; 1-2 interspaces length; rib or vertebral abnormalities in 50%; lower HU than muscle in 70%; 1/3 with NF has NFtosis
asymptomatic /compression. MR is very useful in the exclusion of intraspinal tumor extension, a critical assessment prior to surgical excision. Schwannomas are benign neoplasms, and while malignant degeneration is reported, it is very rare. Affected patients are typically cured after complete surgical excision.

Neurogenic Tu: Symp Ganglia

Gneuroma; GNBlastoma; NBlastoma; oblong paravertebral mass; Ca++ 20%; children 20% of post mass

Neurogenic Tu: Paraganglioma(chemodectoma)

mc APW maybe in post M or atria, from autonomous ganglia; on CT dense enhancement!; compression of M structures -> symptoms; 131-I-MIBG fo rcatecholamine producing tu; octreotide scintigraphy; 10% M and invasive ;resection; local recurrence is common in APW.


ant or lat; assoc w NFsis; herniation of spinal meninges through intervertebral foramen


paravertebral mass in patients with severe anemia ( thalassemia, SCA). Lobulated paravertebral masses, multiple and bilateral, well marginated soft tissue HU ( 30-65)

Thoracic Spine abnormalities

tu, spondilitis; # w hemorhage; bilateral, fusiform.

Enhancing M mass

ly nodes/ Thyroid Parathyroid lesion/carcinoid/lynphangioma/hemangioma/paraganglioma. Diff to diff M mass from ly nodes


extrathoracic uncommon 3% ( head neck/breast/GI/breast/melanoma)

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