Masses of the Anterior Mediastinum A Tale of Four...

Masses of the Anterior Mediastinum A Tale of Four T’s

Victoria Croog, Harvard Medical School--Year IIIGillian Lieberman, MD

November 2000Victoria CroogGillian Lieberman, MD

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Anatomy of the Mediastinum

• Mass lesions of mediastinum occur in PREDICTABLE LOCATIONS according to tissue of origin. Therefore…

Localization of mass is of prime diagnostic importance!!!Localization of mass is of prime diagnostic importance!!!

• Divided into 3 anatomical compartments1. Anterior2. Middle3. Posterior

LOCATION! LOCATION! LOCATION!

Victoria CroogGillian Lieberman, MD

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Anterior MediastinumAnterior border• sternum

Posterior border• ventral cardiac surface and

brachiocephalic vessels

Contents– thymus– fat– lymph nodes– sternum, anterior ribs

From Brad H. Thompson, M.D. http://www.vh.org/Providers/Lectures/icmrad/chest/parts/Mid.Med.html


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Middle MediastinumAnterior Border• ventral heart borderPosterior Border• anterior surface of spineContents

– heart and pericardium– ascending aorta and arch of aorta– vena cavae– brachiocephalic vessels– main pulmonary aa. and vv.– trachea and bronchi– esophagus– lymph nodes



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Posterior MediastinumAnterior Border• anterior surface of spinePosterior Border• posterior ribsContents

– descending aorta– spine and posterior ribs– nerves, ganglia, roots and

spinal cord– lymph nodes– azygous and hemiazygous vv.



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Approach to Mediastinal Masses

1. PA and lateral chest films: From which mediastinal compartment does the mass arise?

2. CT (or MRI) to better characterize nature and extent of lesion. (MRI especially good at looking for spinal canal invasion in masses of posterior mediastinum.)

3. Tissue Biopsy for definitive Dx

However: Unless the patient is symptomatic, the However: Unless the patient is symptomatic, the finding of finding of mediastinalmediastinal mass is often incidental!!!mass is often incidental!!!


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DDx: Anterior Mediastinal Mass “THE FOUR T’S”THE FOUR T’S”


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DDx: Anterior Mediastinal Mass “THE FOUR T’S”THE FOUR T’S”

• Thymoma (or variant thereof)• Teratoma• Thyroid (ectopic)• “Terrible” Lymphoma


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PATIENT 143 y/o female w/ Hx of asthma presents with SOB x 5 days. No wheeze or cough, EKG wnl. CXR ordered to w/u ? infiltrate or pneumothorax…

BIDMC


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Patient 1:FRONTAL CXR

FILM FINDINGS:

•mass in left mediastinum obscures/ is continuous with L cardiac contour

•L pulmonary hilar vessels can be seen separately

•descending aorta is visualized as distinct from mass

BIDMC


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Patient 1: LATERAL CXRFILM FINDINGS:

•mass fills retrosternal space

A CT was ordered to further characterize the mass…

BIDMC


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Patient 1: CHEST CTFILM FINDINGS:Mass just lateral to main pulmonary artery:•thick-walled•smoothly-marginated• fatfat-containing (Hounsfield of -60)•no calcifications

An MRI (not indicated!) was ordered for further characterization…

BIDMC


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Patient 1: CHEST MRI

Mass has high signal intensity on T1… …with suppression of

signal on T1 fat-saturation sequence.

This suggests a fat-containing lesion. Likely diagnosis?

BIDMC BIDMC

T1 T1 FAT SATURATION


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Patient 1:ThymolipomaPatient 1:Thymolipoma

• rare, benign, slow-growing• wide age range, but mean age = 27 yrs• male = female• 50% asymptomatic• composed of mature adipose cells and thymic tissue• large, may occupy both hemithoraces, conforms to

adjacent structures (may mimic cardiomegaly!)• CT/MRI: combination of fat and soft tissue• Rx: Surgical excision


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Differential Diagnosis of Diseases of the Thymus

• Thymoma• Thymic Carcinoma• Thymic Carcinoid• Thymic Cyst• Thymolipoma


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ThymomaThymoma

• most common primary neoplasm of anterior mediastinum• age > 40, male = female• most asymptomatic; 1/3 Sx of compression or invasion of

adjacent structures (chest pain, cough, dyspnea)• parathymic syndromes

– 30-50% myasthenia gravis– less common– hypogammaglobulinema (10%), pure red cell

aplasia (5%)• most encapsulated; 35% invasive (but histologically

benign!)


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ThymomaThymoma (continued)

•• Plain filmPlain film: – well-defined, rounded or lobulated, smooth borders– occurring anywhere from thoracic inlet to diaphragm– calcification RARE

•• CTCT:– well-defined– +/- hemorrhage, necrosis, cyst– if invasive, can seed pleural space and mimic mesothelioma;

can also extend transdiaphragmatically•• RxRx: complete surgical resection – usually good prognosis

– 2-12% of resected encapsulated thymomas recur– invasive thymoma has much worse prognosis– 50% 5-yr

survival, compared to 75% in noninvasive.


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PATIENT 240 y/o female s/p MVA with ? of contusion on CXR…

BIDMC BIDMC

Left anterior mediastinal mass

Not typical for trauma, CT indicated


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Patient 2: CHEST CTA CT was ordered to further characterize the mass:

BIDMC Mediastinal window

Film findings:

large, inhomogeneous, solid, antero-left mediastinal mass. No calcium. No fat.

MASSMASS


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Patient 2: CHEST CT

Film findings:

large, inhomogeneous, solid, antero-left mediastinal mass. No calcium. No fat.

BIDMC

MASS


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PATHOLOGY

A percutaneous biopsy was performed under CT guidance

Pathology reported the presence of Reed- Sternberg cells.

What is the diagnosis?What is the diagnosis?


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Hodgkin’s LymphomaHodgkin’s Lymphoma

• Lymphomas account for 10-20% anterior mediastinal masses– 65-85% Hodgkin’s lymphoma is intrathoracic at presentation,

although isolated mediastinal disease uncommon

• bimodal incidence: 20-30 yrs and 50-70yrs; male = female

• often asymptomatic (as in our patient)– local mass effect of invasion may cause cough, chest pain– if disseminated, constitutional Sx + cervical/ supraclavicular LAP

• in adults, most common is nodular sclerosing Hodgkin’s Disease (NSHD)


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Hodgkin’s Lymphoma (cont)Hodgkin’s Lymphoma (cont)

• CXR:– lobulated– obliterates retrosternal space– 50% thymic involvement– 15% LAP elsewhere in chest– secondary signs of pleural effusion or sternal erosion common– calcification RARE

• CT:– heterogeneous attenuation– solid mass may be enlarged, matted, coalesced lymph nodes– +/- necrosis, hemorrhage, cystic lesions, local invasion


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Hodgkin’s Lymphoma (cont 2)Hodgkin’s Lymphoma (cont 2)

• Dx: Biopsy: percutaneous, thoracotomy or mediastinoscopy

• Rx: Chemotherapy or XRT

• Prognosis: Varies with tumor histology


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PATIENT 318 y/o female with R upper chest and shoulder pain x 1 month. Exacerbated by movement and inspiration. No findings on PE. Working Dx is musculoskeletal injury. A CXR was ordered…

http://www.vh.org/Providers/TeachingFiles/TAP/Cases/Case38/Case38.html

right anterior mediastinal mass


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Patient 3: CHEST CTA CT was ordered for further characterization.

CT shows mass with areas of:

•fat

•fluid

•soft tissue

Likely Likely diagnosis?diagnosis?

http://www.vh.org/Providers/TeachingFiles/TAP/Cases/Case38/Case38.html


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PATHOLOGY

A percutaneous biopsy was performed under CT guidance.

Pathology: Teratoma with pancreatic and thymic tissues


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Patient 3: Germ Cell Tumor (GCT)Patient 3: Germ Cell Tumor (GCT)•Mediastinum most common extra-gonadal site for GCT’s

•GCT’s = 10-15% anterior mediastinal masses

•Primitive germ cells “misplaced” in mediastinum during embryogenesis

•mean age = 27 years

•80% benign (male = female)

•20% malignant: more common in males (9:1) with poor Px

•Teratoma >> Seminoma, Nonseminomatous Malignant GCT’s


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GCT: GCT: TeratomaTeratoma

• mature teratoma = 60-70% of mediastinal GCT• usually asymptomatic; mass effect may result in

chest pain, dyspnea, cough• CXR:

– well-circumscribed, round or lobulated– calcifications in up to 26%

• CT:– well-marginated, lobulated– cystic component 88%, fat 50-75%, calcification 25-

50%– fat-fluid levels diagnostic, but rare (<10%)

• Surgical excision is curative


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PATIENT 4

http://www.mamc.amedd.army.mil/WILLIAMS/CHEST/Mediastinum/Left.htm

History omitted.


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PATIENT 4


Film Findings

•Trachea deviated to right

•Left anterosuperior mediastinal mass extending into cervical region


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Patient 4: CHEST CT


A chest CT was ordered for further characterization.

M = Mass

M M

Likely diagnosis?Likely diagnosis?


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Patient 4: Patient 4: MediastinalMediastinal GoiterGoiter

• 10% of mediastinal masses• 20% cervical goiters descend into thorax–

left anterior superior mediastinum• primary intrathoracic goiter without cervical

component very rare!• asymptomatic w/ palpable cervical goiter• occasionally, Sx of compression or pain• female:male = 4:1


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MediastinalMediastinal Goiter (cont)Goiter (cont)

• CXR:– smooth displacement of trachea (or esophagus)

+/- narrowing– calcification COMMON

• I-131 Scan:– diagnostic when functioning thyroid tissue

present!– false negatives – if neg. scan but high clinical

suspicion, do CT…


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MediastinalMediastinal Goiter (cont 2)Goiter (cont 2)

• CT– continuity w/ cervical thyroid– well-defined, lobulated, encapsulated– coarse, punctate or ring-like calcification– discrete areas of low attenuation = hemorrhage, cyst– discrete areas of high attenuation = intrinsic iodine

• Rx– if Sx, surgical resection


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Diagnosing Masses of the Anterior Mediastinum

• many serendipitously discovered on CXR• some present w/ vague chest complaints or

signs/Sx of compression/ invasion• most common are the “FOUR T’S”

– thymoma– teratoma– thyroid– “terrible” lymphoma… all others lesions are extremely rare!!


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Diagnosing Masses of the Anterior Mediastinum

• if thymoma, evaluate for myasthenia gravis to avoid post-op respiratory failure

• do a thorough PE to exclude cervical goiter and to detect occult lymphadenopathy

• CT is mainstay for f/u– confidently Dx mature teratoma, mediastinal

goiter– evaluate adjacent structures for mass effect or

invasion• Biopsy is definitive!


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Other Mediastinal Masses Middle Middle MediastinumMediastinum

MIDDLE = “A + B”

• Adenopathy– infection (TB, Histoplasmosis, Coccidioidomycosis)– inflammatory (Sarcoid, Silicosis)– neoplasm (leukemia/ lymphoma, metastases)

• Bronchopulmonary (foregut) malformations


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Other Mediastinal Masses Posterior Posterior MediastinumMediastinum

POSTERIOR = “3 N’s”• Neurogenic masses

– nerve root tumors (schwannoma, neurofibroma)– sympathetic ganglion tumors (neuroblastoma,

ganglioneuroma, ganglioneuroblastoma)– paragangliomas (pheochromocytoma)– neurenteric cysts

• Nodes• aNeurysm (of descending aorta)


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REFERENCES

http://www.indyrad.iupui.edu/rtf/teaching/medstudents

http://www.mamc.amedd.army.mil/WILLIAMS/CHEST

http://www.vh.org/Providers/TeachingFiles/TAP/Cases

Ronson R, Duarte I, Miller J. Embryology and surgical anatomy of the mediastinum with clinical implications. Surgical Clinics of North America, Vol (80), Number 1, 2000.

Rosado M. The AFIP Lecture Series: Mediastinal Masses. http://radpath.org/syllabus/chest/rosado/medmas.html

Strollo D, Rosado M, Jett J. Primary Mediastinal Tumors. Chest, Vol (112), Number 2, 1997.

Thompson B. Virtual Hospital: Introduction to Clinical Radiology: Chest: Normal Anatomy. http://www.vh.org/Providers/Lectures/icmrad/chest/parts


http://www.indyrad.iupui.edu/rtf/teaching/medstudents

http://www.mamc.amedd.army.mil/WILLIAMS/CHEST

http://www.vh.org/Providers/TeachingFiles/TAP/Cases

http://radpath.org/syllabus/chest/rosado/medmas.html

http://www.vh.org/Providers/Lectures/icmrad/chest/parts

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Acknowledgements

Special thanks to Eric Chiang, M.D.

Beverlee Turner for her support and PowerPoint expertise

Larry Barbaras and Ben Crandall our WebMasters

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Masses of the Anterior Mediastinum A Tale of Four...

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