systematic approach to fat containing lesions of the...
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Systematic Approach To Fat Containing Lesions Of The Thorax
Ernest Yushvayev, Daniel Droukas, Robert Perone.
Northwell Health
Disclosure statement
We have no actual or potential conflicts of interest in relation to this electronic exhibit.
Goals
1. To become familiar with a variety of fat containing intra-thoracic lesions.
2. Learn to easily narrow the differential diagnosis based on the imaging characteristics and location within specific compartments of the thorax.
Objectives
1. To identify fat containing lesions and their imaging characteristics.
2. To review intrathoracic examples of such lesions.
Target Audience
This electronic presentation is geared towards Radiology residents.
Imaging of fat and patterns of distribution
Macroscopic fat on CT
-10 to -100 Hounsfield units.
Fat on MRI
Hyperintense on T1 weighted images and intermediate to hyperintense on T2 weighted images.
Fat on Ultrasound
Echogenic
Patterns of fat distribution
Homogenous
Focal
Heterogenous
Endobronchial Lesions
● Bronchogenic adenocarcinoma
● Squamous cell carcinoma● Small cell carcinoma● Bronchial carcinoid● Endobronchial metastasis● Leiomyoma● Squamous cell papilloma● Pleomorphic adenoma● Granular cell tumor● Amyloidoma● Fibroepithelial polyp
● Hamartoma● Lipoma
FAT?
NO YES
Image courtesy of e-Anatomy, Micheau A, Hoa D, www.imaios.com
ENDOBRONCHIAL FAT CONTAINING LESIONS
Hamartoma
Symptoms: Obstructive in nature, including chronic cough, hemoptysis and fever.Contents: Cartilage, fat, fibrous and epithelial tissue.CT findings: Postobstructive changes. Smooth bordered endobronchial lesion with alternating foci of fat and calcification.
Lipoma
Benign. Predilection for mainstem bronchi.Symptoms: Post obstructive symptoms. Chest pain, dyspnea, fevers, pneumonia.CT findings: Postobstructive changes. Pedunculated homogenous lesion with fat attenuation (approximately -100 HU)Figure 1: Endobronchial hamartoma: Heterogenous endobronchial lesion with areas of fat attenuation in the right middle lobe bronchus. Post obstructive atelectasis is noted in the right middle lobe. Case courtesy of H. Page McAdams, MD, Duke University Medical Center, Durham, NC.
Intraparenchymal Lesions
Broad differential including malignant, benign, infectious, vascular and inflammatory etiologies.
● Hamartoma● Lipoma● Lipoid Pneumonia
FAT?
NO YES
Image courtesy of e-Anatomy, Micheau A, Hoa D, www.imaios.com
INTRAPARENCHYMAL FAT CONTAINING LESIONS
Hamartoma
Benign. Male Predominance of 2:1 to 3:1.Location: Most common in the hilar region.CT findings:
● Soft tissue mass or nodule● Popcorn calcification (5-50%)● Focal or generalized fat (50%)
Lipoma
Origin: Adipose tissue.Asymptomatic, rare and benign.CT findings:
● Well circumscribed lesion.● Homogenous fat attenuation.
Figures 2 a,b,c,d: Intraparenchymal Hamartoma. Right hilar mass with punctate focus of calcification and focal areas of fat.
A B
C D
INTRAPARENCHYMAL FAT CONTAINING LESIONS
Lipoid Pneumonia
Etiology: ● Exogenous: Acute or chronic aspirations of
oils.● Endogenous: Secondary to a central
obstructive lesion. Pathophysiology:
● Macrophage phagocytosis within alveoli and eventual transport to interlobular septa.
● Local edema and inflammation which may progress to fibrosis.
CT findings:● Predominantly involve middle and lower lobes.● Mass like ground glass or consolidative
opacities with areas of fat attenuation.● Crazy paving pattern may be seen.● Fibrotic changes such as traction
bronchiectasis. Figure 3 a,b: Lipoid Pneumonia. Mass like consolidation in the left lower lobe with focal area of fat.
A
B
Mediastinal Lesions
Anterior Mediastinum-Thymic Masses-Germ Cell Tumors-Thyroid Masses-Lymph Node Masses-Vascular -Parathyroid Masses
-Thymolipoma-Teratoma and Teratocarcinoma-Mesenchymal lesions such as lipomatosis and lipoma.-Extramedullary Hematopoiesis-Esophageal lipoma-Lipoblastoma-Liposarcoma
FAT?
NO YES
MIddle Mediastinum-Lymph Node Masses-Duplication Cyst-Vascular
Posterior Mediastinum-Neurogenic Masses-Vascular-Duplication Cyst-Neurenteric cyst-Lymph node masses
Image courtesy of e-Anatomy, Micheau A, Hoa D, www.imaios.com
MEDIASTINAL FAT CONTAINING LESIONS
Lipoma
Origin: Mesenchymal tumor originating from adipose tissue.Symptoms: Secondary to mass effect.Location: Most common in anterior mediastinumCT findings:
● Well circumscribed mass● Homogenous fat attenuation
Lipomatosis
Seen in exogenous steroid use and obesity.CT Findings:
● Unencapsulated● Infiltrating fat
Figure 4a: Mediastinal Lipomatosis. Figure 4b: Mediastinal Lipoma.
Figure 4a
Figure 4b
A
B
MEDIASTINAL FAT CONTAINING LESIONS
Thymolipoma
Rare and benign anterior mediastinal lesionSymptoms: Mass effect. Typically asymptomatic.CT findings:
● Well delineated mass● Fat attenuation mixed with normal thymic
tissue● Connection to thymus or superior mediastinum
can often be demonstrated.
Figures 5a, 5b: Thymolipoma: Well circumscribed mass in the anteriormediastinum, anterior to the aortic arch which demonstrates mixed fat andsoft tissue density.
Figure 5a
Figure 5b
A
B
MEDIASTINAL FAT CONTAINING LESIONS
Teratoma
Origin: Germ CellMediastinal Location: Typically Anterior.Histology: Mature ( Benign) Immature ( Malignant) CT findings:
● Heterogeneous cystic lesion● Smooth Contoured, encapsulated, multicystic● Calcification. ● Soft tissue component.● Fat component( 76% of cases)● Fat fluid level.
Teratocarcinoma
Male Predilection CT findings: Above findings with following differences
● Poorly defined, irregular and nodular margins.● Thick enhancing capsule with contrast admin.
Figure 6a: Teratoma: Anterior mediastinal cystic mass with soft tissue, fluid, fat and calcium components.
Figure 6b: Teratocarcinoma:Anterior mediastinal mass with soft tissue and fat component. Nodular and irregular margin.
A
B
MEDIASTINAL FAT CONTAINING LESIONS
Lipoblastoma
Origin: MesenchymalAge: Early childhoodLocation: Typically in the extremities ( 70%). Can also be seen in the mediastinum as well as other locations..Symptoms: Secondary to mass effect.CT Findings:
● Mostly fatty mass● Well defined margins● Can have septa and nodularity● Intratumoral stranding ● Cystic changes can be seen.
MRI Findings:● Intratumoral streaks and whorls
Figure 4a
Figure 4b
Figure 7a:Lipoblastoma. 7 year old patient. CT shows a heterogenous fatty lesion . Thoracic inlet is a characteristic location for lipoblastoma.Case courtesy of Mark J. Kransdorf, MD, Mayo Clinic, Jacksonville, Fla.
Figure 7b:Lipoblastoma.Coronal T1 weighted image. Heterogeneous fatty lesion at the right thoracic inlet. Internal streaks and whorls are demonstrated which are representative of its characteristic fibrovascular network. Case courtesy of Mark J. Kransdorf, MD, Mayo Clinic, Jacksonville, Fla.
A
B
Cardiac Lesions
● Myxoma● Papillary fibroelastoma● Rhabdomyoma● Fibroma● Hemangioma● Paraganglioma● Sarcomas● Primary cardiac lymphoma● Pericardial Mesothelioma
● Lipoma● Liposarcoma● Lipomatous Hypertrophy of
the interatrial septum● Arrhythmogenic right
ventricular dysplasia
FAT?
NO YES
Image courtesy of e-Anatomy, Micheau A, Hoa D, www.imaios.com
CARDIAC FAT CONTAINING LESIONS
Lipoma
Location: Typically Extra Myocardial. Can be either subendocardial or subepicardial.Symptoms: Secondary to mass effect. Include: anginal pain, arrhythmia, sudden death and CHF.CT findings:
● Encapsulated oval fat attenuation mass.
Figure 8: Cardiac Lipoma: Well marginated fat attenuation lesion along the right atrial wall.
CARDIAC FAT CONTAINING LESIONS
Liposarcoma
MalignantLocation: Typically right side of heart. Behavior: Local invasion or metastasis.Histology: Well differentiated, myxoid, round cell, pleomorphic.Symptoms: Chest pain, dyspnea, arrhythmia, symptoms of CHF.Imaging findings:
● Mass with varying fat content ranging from homogeneously fatty to nearly complete soft tissue attenuation.
● Signs of invasion or infiltration.● Calcification.● Adjacent mediastinal structure may have
poorly defined margins.
Figure 9a, 9b: Well differentiated liposarcoma: Axial T2 and coronal T1 weighted MR images demonstrate a lobular hyperintense mass along the right heart border. Case courtesy of Mark J. Kransdorf, MD, Mayo Clinic, Jacksonville, Fla.
A
B
CARDIAC FAT CONTAINING LESIONS
Lipomatous Hypertrophy of the Interatrial Septum
BenignUnencapsulated fat containing lesion in the interatrial septum.No extracardiac or intracavitary component. Symptoms: Asymptomatic. Maybe associated with arrhythmias or sudden cardiac death. Imaging findings:
● Fat containing lesion in the interatrial septum.● Characteristic dumbbell shape.● Nonenhancing.● Well marginated, non encapsulated.● Relative sparing of oval fossa.● Moderate FDG uptake on PET/CT
Figure 10a: Lipomatous hypertrophy of the interatrial Septum. Well marginated fat containing lesion in the interatrial septum. Figure 10b shows a T1 weighted MRI image in which sparing of the oval fossa and characteristic dumbbell shape is demonstrated.
A B
CARDIAC FAT CONTAINING LESIONS
Arrhythmogenic Right Ventricular Dysplasia (ARVD)
Fatty or fibrofatty replacement of the right ventricular myocardial tissue.Location: Right ventricular apex is the most commonly affected.Symptoms: Ventricular arrhythmias or sudden cardiac death. Imaging findings:
● Fatty or fibrofatty replacement of the right ventricular myocardium.
● Diffuse or focal right ventricular dilatation.● Right ventricular wall thinning● MR cine imaging can show wall motion
abnormalities and lack of normal systolic thickening.
Figure 11a ARVD: Axial Fast Spin echo T2 weighted MR image demonstrates fatty replacement of the myocardium in the right ventricular apex. ( Black Arrows) Case courtesy of David A. Lynch, MD, University of Colorado Health Sciences Center, Denver.
Figure 11b, c ARVD: Cine MR images at end systole (b) and end diastole(C) demonstrate lack of normal systolic wall thickening and akinesis of the right ventricular wall. Case courtesy of David A. Lynch, MD, University of Colorado Health Sciences Center, Denver.
A
B C
Solid Pleural and Extrapleural Lesions
-Pleural Thickening-Localized fibrous tumor of the pleura-pleural Metastasis-Lymphoma-Lung Cancer with chest wall invasion-Splenosis-Mesothelioma-Askin tumor
-Lipoma-Hiatal Hernia-Bochdalek Hernia-Morgagni Hernia-Juxtacaval Fat
FAT?
NO YES
Image courtesy of e-Anatomy, Micheau A, Hoa D, www.imaios.com
PLEURAL FAT CONTAINING LESIONS
Lipoma
Benign encapsulated fatty tumorOrigin: submesothelial layer of the parietal pleura.Symptoms: Typically asymptomatic. Can be associated with with cough, back pain, exertional dyspnea. CT findings:
● Well circumscribed.● Homogenous fat attenuation.
Figure 12 Pleural Lipoma
EXTRAPLEURAL FAT CONTAINING LESIONS
Morgagni Hernia
Herniation of abdominal contents through a diaphragmatic defect termed foramen of Morgagni. Location: Anterior and retrosternal. Right sided (90% of the cases)Hernia contents: omentum> colon>stomach> liver >small intestine.
CT findings:● Sagittal or coronal images can assist in
demonstrating the diaphragmatic defect.
Figure 13 a, b: Morgagni Hernia. Axial and sagittal images demonstrate right sided, anterior and retrosternal herniation of bowel and omental fat. Sagittal image demonstrates diaphragmatic defect.
Figure 4a
Figure 4b
A
B
EXTRAPLEURAL FAT CONTAINING LESIONS
Bochdalek Hernia
Developmental defect in posterior portion of the diaphragm results in herniation of abdominal contents.Presentation: InfancyLaterality: Left sided ( 70-90% of cases)Contents: Typically fat and omental tissue. Retroperitoneal and intraperitoneal contents may also herniate.CT findings:
● Sagittal or coronal images can assist in demonstrating the diaphragmatic defect.
Figure 4a
Figure 4b
Figure 14 a,b: Bochdalek Hernia. Axial and coronal images demonstrate right sided paraspinal lesion with fat attenuation. Coronal image demonstrates the diaphragmatic defect.
A
B
EXTRAPLEURAL FAT CONTAINING LESIONS
Juxtacaval Fat
Focal fat collection medial to and adjacent to the lumen of the IVC near the hepatic venous junction. CT appearance:
● Focal lesion with fat density adjacent to and medial to IVC● Can appear to be intracaval. Attributed to
subdiaphragmatic narrowing of the IVC.
Figure 15: Juxtacaval Fat. Homogeneous lesion with fat attenuation, appears to be within the lumen of the IVC at the level of the hepatic venous junction.
Figure 4a
Figure 4b
Conclusion
Identifying fat containing intra-thoracic lesions and their anatomic location within the thorax can assist the radiologist in narrowing the differential so that a more accurate radiologic diagnosis can be made thus facilitating the implementation of prompt and appropriate patient management.
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