Systematic Approach to Fat Containing Lesions of the Thorax

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. 1. To identify fat containing lesions and their imaging Objectives 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 Patterns of fat distribution

-10 to -100 Hounsfield units.

Fat on MRI Homogenous Hyperintense on T1 weighted images and intermediate to hyperintense on T2 weighted images.

Fat on Ultrasound Focal Echogenic

Heterogenous Endobronchial Lesions

FAT?

NO YES

● Hamartoma ● Bronchogenic ● Lipoma adenocarcinoma ● Squamous cell carcinoma ● Small cell carcinoma ● Bronchial carcinoid ● Endobronchial metastasis ● Leiomyoma ● Squamous cell papilloma ● Pleomorphic adenoma ● Granular cell tumor ● Amyloidoma ● Fibroepithelial polyp 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

FAT?

NO YES

● Hamartoma Broad differential including ● Lipoma malignant, benign, infectious, ● Lipoid Pneumonia vascular and inflammatory etiologies.

Image courtesy of e-Anatomy, Micheau A, Hoa D, www.imaios.com A B 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%) D C 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. INTRAPARENCHYMAL FAT CONTAINING A 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 B 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. Mediastinal Lesions

FAT?

NO YES

-Thymolipoma Anterior Mediastinum MIddle Mediastinum -Teratoma and Teratocarcinoma -Thymic Masses -Lymph Node Masses -Mesenchymal lesions such as lipomatosis -Germ Cell Tumors -Duplication Cyst and lipoma. -Thyroid Masses -Vascular -Extramedullary Hematopoiesis -Lymph Node Masses -Esophageal lipoma -Vascular Posterior Mediastinum -Lipoblastoma -Parathyroid Masses -Neurogenic Masses -Liposarcoma -Vascular -Duplication Cyst -Neurenteric cyst -Lymph node masses

Image courtesy of e-Anatomy, Micheau A, Hoa D, www.imaios.com Figure 4a

MEDIASTINAL FAT CONTAINING LESIONS A

Lipoma

Origin: Mesenchymal tumor originating from adipose tissue. Symptoms: Secondary to mass effect. Location: Most common in anterior mediastinum CT findings: ● Well circumscribed mass ● Homogenous fat attenuation

FigureB 4b Lipomatosis

Seen in exogenous steroid use and obesity. CT Findings: ● Unencapsulated ● Infiltrating fat

Figure 4a: Mediastinal Lipomatosis. Figure 4b: Mediastinal Lipoma. MEDIASTINAL FAT CONTAINING LESIONS FigureA 5a

Thymolipoma

Rare and benign anterior mediastinal lesion Symptoms: 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. B Figure 5b

Figures 5a, 5b: Thymolipoma: Well circumscribed mass in the anterior mediastinum, anterior to the aortic arch which demonstrates mixed fat and soft tissue density. Figure 6a: Teratoma: Anterior mediastinal cystic mass with soft A tissue, fluid, fat and calcium MEDIASTINAL FAT CONTAINING LESIONS components.

Teratoma

Origin: Germ Cell Mediastinal Location: Typically Anterior. Histology: Mature ( Benign) Immature ( Malignant) CT findings: ● Heterogeneous cystic lesion ● Smooth Contoured, encapsulated, multicystic B Figure 6b: ● Calcification. Teratocarcinoma:Anterior mediastinal mass with soft tissue ● Soft tissue component. and fat component. Nodular and ● Fat component( 76% of cases) irregular margin. ● 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 4a Figure 7a:Lipoblastoma. 7 year old patient. CT shows a heterogenous fatty lesion . MEDIASTINAL FAT CONTAINING LESIONS A Thoracic inlet is a characteristic location for lipoblastoma.Case courtesy of Mark J. Kransdorf, MD, Lipoblastoma Mayo Clinic, Jacksonville, Fla. Origin: Mesenchymal Age: Early childhood Location: Typically in the extremities ( 70%). Can also be seen in the mediastinum as well as other locations.. Symptoms: Secondary to mass effect.

CT Findings: Figure 7b:Lipoblastoma. BFigure 4b Coronal T1 weighted image. ● Mostly fatty mass Heterogeneous fatty lesion ● Well defined margins at the right thoracic inlet. Internal streaks and whorls ● Can have septa and nodularity are demonstrated which are representative of its ● Intratumoral stranding characteristic fibrovascular network. Case courtesy of ● Cystic changes can be seen. Mark J. Kransdorf, MD, MRI Findings: Mayo Clinic, Jacksonville, Fla. ● Intratumoral streaks and whorls Cardiac Lesions

FAT?

NO YES

● Lipoma ● Myxoma ● Liposarcoma ● Papillary fibroelastoma ● Lipomatous Hypertrophy of ● Rhabdomyoma the interatrial septum ● Fibroma ● Arrhythmogenic right ● Hemangioma ventricular dysplasia ● Paraganglioma ● Sarcomas ● Primary cardiac lymphoma ● Pericardial Mesothelioma

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. Figure 9a, 9b: Well differentiated liposarcoma: A Axial T2 and coronal T1 CARDIAC FAT CONTAINING LESIONS weighted MR images demonstrate a lobular hyperintense mass along the right heart border. Case Liposarcoma courtesy of Mark J. Kransdorf, MD, Mayo Clinic, Jacksonville, Fla. Malignant Location: 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. B 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. A B CARDIAC FAT CONTAINING LESIONS

Lipomatous Hypertrophy of the Interatrial Septum

Benign Unencapsulated fat containing lesion in the interatrial septum.

No extracardiac or intracavitary component. Figure 10a: Lipomatous hypertrophy of the interatrial Septum. Well marginated fat containing lesion in the interatrial Symptoms: Asymptomatic. Maybe associated with septum. Figure 10b shows a T1 weighted MRI image in which arrhythmias or sudden cardiac death. sparing of the oval fossa and characteristic dumbbell shape is demonstrated. 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 11a ARVD: Axial Fast Spin echo T2 weighted MR CARDIAC FAT CONTAINING LESIONS A image demonstrates fatty replacement of the myocardium in the right ventricular apex. ( Black Arrhythmogenic Right Ventricular Dysplasia Arrows) Case courtesy of David A. Lynch, MD, University (ARVD) of Colorado Health Sciences Center, Denver. 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. B C 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 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 thickening. A. Lynch, MD, University of Colorado Health Sciences Center, Denver. Solid Pleural and Extrapleural Lesions

FAT?

NO YES

-Lipoma -Pleural Thickening -Hiatal Hernia -Localized fibrous tumor of the -Bochdalek Hernia pleura -Morgagni Hernia -pleural Metastasis -Juxtacaval Fat -Lymphoma -Lung Cancer with chest wall invasion -Splenosis -Mesothelioma -Askin tumor

Image courtesy of e-Anatomy, Micheau A, Hoa D, www.imaios.com PLEURAL FAT CONTAINING LESIONS

Lipoma

Benign encapsulated fatty tumor Origin: 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 Figure 4a

EXTRAPLEURAL FAT CONTAINING LESIONS A

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 B >small intestine. Figure 4b 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 A EXTRAPLEURAL FAT CONTAINING LESIONS

Bochdalek Hernia

Developmental defect in posterior portion of the diaphragm results in herniation of abdominal contents. Figure 14 a,b: Bochdalek Hernia. Axial and Presentation: Infancy coronal images demonstrate right sided paraspinal lesion with fat attenuation. Laterality: Left sided ( 70-90% of cases) Coronal image demonstrates the Contents: Typically fat and omental tissue. diaphragmatic defect. Retroperitoneal and intraperitoneal contents may BFigure 4b also herniate. CT findings: ● Sagittal or coronal images can assist in demonstrating the diaphragmatic defect. Figure 4a

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 4b

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. 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. References

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