Imaging of anterior and middle mediastinal

masses

G Ferretti S Lantuejoul Radiologie Centrale et Imagerie Médicale Anatomopathologie CHU Grenoble

Objectives

n  To present the last version of mediastinal compartments

n  To show the useful signs to characterize mediastinal masses on CT or MR

n  To describe the more common masses based on density or signal and location

Detection of mediastinal masses: CXR

n  displaced n  enlarged n  abnormal contours

•  lines •  bands •  interfaces

Based on: n  Mass effect n  Abnormal contours of the mediastinum

Mediastinal lines: limites

Les lignes médiastinales ne sont pas constamment visibles (Proto JTI 1987; 2: 47) :

1. Ligne médiastinale postérieure 15%

2. Ligne médiastinale antérieure 60%

3. Interface aortique descendant 100%

4. Ligne paravertébrale gauche 65%

5. Ligne paravertébrale droite 40%

6. Bande para trachéale droite 97%

7. Bouton azygos 98%

8. Bande para oesophagienne 90%

n  Several traditional mediastinal division schemes exist based upon arbitrary landmarks on the lateral chest radiograph (anatomy, surgical, radiology)

n  However, CT has replaced CXR and this group proposed a new division of the mediastinum based on CT landmarks

n  Localization of a tumor within one of the compartments of the mediastinum n  Narrows the differential diagnosis n  Gives a probability of malignancy of the tumor n  Assist in planning histological sampling n  Assist in planning surgery

International thymic malignancy interest group

Number of Compartments

n  This clinical classification defines 1.  a prevascular (anterior) compartment 2.  a visceral (middle) compartment 3.  a paravertebral (posterior) compartment

n  with anatomic boundaries defined clearly by CT

ITMIG compartiments of mediastinum

n  prevascular (anterior)

n  visceral (middle) n  paravertebral (posterior)

n  Posterior limit of the anterior mediastinum is the anterior aspect of the pericardium as it wraps around in a curvilinear fashion (thus any vessels contained within the pericardium are located in the middle mediastinum)

n  contents of the prevascular compartment : the thymus, fat, lymph nodes, and the left brachiocephalic vein.

n  Boundaries of visceral mediastinum n  anteriorly—the anterior aspect of the pericardium

n  posteriorly—a vertical line connecting a point on the thoracic vertebral bodies 1 cm posterior to the anterior margin of the spine

Localization of Mediastinal Abnormalities: CT MRI two tools are useful: 1. the “center method.” the center of a mediastinal

lesion localizes the abnormality to a specific compartment.

2. the “structure displacement tool.” Very large

mediastinal masses can displace organs from other compartments, usually those that abut the compartment from which the tumor originated.

Carter BW JTO 2014;9:s97-s101

Goals imaging Ø  Identification and localization Ø  Description and characterization Ø  Accurate differential diagnosis - short list Ø  Recommendation of a cost effective

imaging and patient management Ø  guiding biopsies Ø  planning surgery

Ø Follow-up

Thacker PG J Thorax Imaging 2015;30:247-264

CT ü  Non contrast ü  Arterial phase ü  Venous phase ü  MIP

MRI ü  T1 ü  T2 / T2 fat sat ü  T1 Gd ü  MR angiography ü  Cardiac gating

Quality control

US Nuclear medicine

PET CT MIBG

CXR

Juanpere S Insight Imaging 2013;4:29-52

CT / MR Fat or fatty lesion

Tissue density

Water containing

Lymph node Vascular origin

Bowel structure

1-Localization Center method

Structure displacement tool

2-Characterization

Fat containing lesions1.6–2.3% of all primary mediastinal tumours

Attenuation – 40 to –130 HU Hyper signal T1

Glazer AJR 1992

anterior mediastinum lipomatosis

60 yo man CXR before aortic surgery. Middle mediastinum lipoma

Giant thymolipoma

18 yo man 3 months coughing

Teratoma benign

Heterogeneity of teratomas Common combinations of internal

components of mature teratomas: n  soft tissue, fluid, fat and calcification 39% n  soft tissue, fluid and fat 24% n  soft tissue and fluid 15% n  non-specific cystic lesions 15% Mature and immature teratomas have the

same presentation

Takahashi K J Magn Reson Imaging 2010; 32:1325–1339

Liposarcoma n  Usually symptomatic n  Can range from

predominantly fatty mass to solid mass with little or no macroscopic fat

n  Differential: lipoma, thymolipoma, mediastinal germ cell tumor.

Fat containing masses

Anterior mediastinum •  teratoma •  lipoma •  thymolipoma •  hibernoma

Anterior cardiophrenic angle •  fat •  Morgani’s hernia •  teratoma •  lipoma •  thymolipoma

Posterior mediastinum •  fat hernia

All compartments •  lipomatosis •  liposarcoma

Cysts and cystic lesionsMediastinal primary cysts: 15–20% of all primary mediastinal masses

Water attenuation (not always) Low signal T1 hyper signal T2

Cyst: no/tiny wall, no tissue thickening, no enhancement of the wall, various density / signal

Cystic tumor

Kim JCAT 2003

Bronchogenic cyst

30 yo woman Esophageal Duplication

Foregut duplication cysts (middle compartment) n  Embryologic origin: Bronchogenic, esophageal,

neurenteric

n  11% of pediatric / 20% of adult mediastinal masses n  only the presence of a vertebral cleft +

mediastinal cyst is specific: neurenteric cyst n  Round / oval smoothly marginated mass n  Tiny / no wall n  50%: hyperintense T2WI or near 0 HU n  Hemorrhage or infection: higher density /signal

and increase in size

1995 2001

Pericardial cyst

Congenital thymic cyst. KYSTE EPITHELIAL thymique bénin de 55 mm de grand axe, développé sur un parenchyme thymique siège de multiples micro-kystes développés au dépens des

corpuscules de Hassal plus ou moins calcifiés. Pas d'élément suspect de malignité.

homme 68 ans 4214

This is not a cyst: the wall is thick and enhanced

Thymoma with cystic component

découvert fortuite préopératoire absence de myasthénie

thymectomie élargie 6*10cm exérèse macroscopique complète

Thymoma with cystic portion 65 yo man

CT for asbestosis exposure Thymoma

Thymic cyt n  1% of all mediastinal masses n  Congenital or acquired (inflammation HIV) n  Rare well defined mass with smooth walls, non

enhancing n  CRX: occult n  CT: not always water density: differential solid

mass n  MR > CT: hypo intense on T1 WI and hyper

intense on T2WI; lack of internal enhancement Ackman JB AJR 2011;197:w15-w20

Lympadenopathy central necrosis tuberculosis

Cystic masses True cysts • Bronchogenic / esophageal • Thymic • Pericardial • Lymphangioma •  Hydatidosis

Masses with cystic component • Thymoma • Teratoma • Lymphoma • Neurogenic T • LAP (BK, metastases)

Pseudo-cysts • pancreatic

Localized • Pleurisy • Pericarditis

other • Meningocele •  lymphocele

Vascular masses

Aneurism of the descending aorta

Oesophageal varices

Soft tissue masses of anterior mediastinum

Strollo Chest 1997 Thacker PG JTO 2014; 30 :247-267

11 ans 17 ans

36 ans 52 ans

Thymus appearance varies with age

Normal Thymus on CT n  Detection: frequency

n  < 30 yo: 100% n  30-50 yo: 70% n  > 50 yo: 20%

n  Thickness n  < 18 mm if age < 25 y but < 13 mm if age > 25 y

n  Smoothly marginated homogeneous gland, no compression. Convex external borders if > 25 y

n  Densité n  Gradual fatty replacement

Nasseri F Radiographics 2010;30:413-428

26 5 2006

13 2 2006 True thymic hyperplasia after stopping chemotherapy.

Diffuse symmetric enlargement of the gland, smooth contour and normal vessels

32 yo woman myasthenia gravis since 4 years 14 mm thick thymus with contrast enhancemement: Thymoma? Hyperplasia? Thymectomy : 28gr thymus with Follicular lymphoid hyperplasia

Woman 53 yo (5100) Thymoma

43 yo man myasthenia gravis (4426) CT: lesion anterior mediastinum 6 x 3.8 cm No fat plane between tumor and aorta Central calcification thymectomy was possible thymoma B3

B3 thymoma with pleural metastases

Pericardial extent of a thymoma

Thymoma n  Rare in children (1-2% prevascular Tumors) n  Frequent in adults > 40yo n  Thymic epithelial tumor with lymphocytes n  40% of patients have paraneoplastic syndrome:

myasthenia n  At histology : invasive / non invasive based of the

integrity of the capsule n  CT/MR are not able to precisely define invasive vs.

noninvasive thymoma +++

CT and thymoma n  2 radiological types : presurgical staging

n  T1 : well limited mass surrounded of mediastinal fat, of limited size and various density: encapsulated thymoma at imaging that may be encapsulated thymomas or thymomas with limited extracapsular extension at pathology. Surgery without biopsy

n  T II : not well limited mass, large size, heterogeneous attenuation, with signs of macroscopic extracapsular extension (medistinum, pleura, pericardial, distant). Surgery may not be curative. Surgery? TT biopsy?

Inaoka T Radiology 2007 243:869-876

Myasthenia and thymus n  At pathology, the thymus of myastenic patients

shows: n  65% follicular lymphoid hyperplasia n  15% thymoma n  20% normal thymus

n  30-50% of thymomas are linked with myasthenia

n  Synchronous ou asynchronous n  25% of patients (woman) are better after thymectomy

Harvard CWH Drugs 1983;26:174-84

Mizuno T Surg Today 1997;27:275-77

MRI n  After CT in some cases n  Not > to CT for local extension or for

prognostic value

Thymic carcinoma 5691

Man 69 yo Paralysie diaphragmatique droite

24 yo man. Mass + AFP : 75000 (Yolk Sac Tumor)

Nonteratomatous germ cell T (NTGCT) n  Seminomatous T of anterior M

n  Large homogenous, lobulated, tumors n  compression of mediastinum

n  Nonseminomatous T of anterior M n  Large heterogeneous tumors n  Invasion of adjacent structures, ADP

n  Accuracy of CT MRI is not good for histology n  Role +++ of biology n  Elevation of α-fetoprotein (AFP) and/or human chorionic gonadotropin

(HCG) support the diagnosis Oldenburg J Ann Oncol 2013;24:125-132

Ectopic goiter

Mediastinal goiter n  direct contiguous growth of a goitre into

the anterior or superior mediastinum. n  encapsulated and lobulated mass with

inhomogeneous appearance (cystic, calcifications, contrast enhancement)

n  Intrathoracic thyroid mass from heterotopic thyroid tissue without any connection to the thyroid in the neck is extremely rare

Lymphoma 2-10% of anterior masses in patients >40 yo n  Hodgkin disease (Reed Sternberg cells) ~70%

n  mediastinal 60%, young patients,

n  NHL T- or B-lymphocytes ~30% n  Large prevascular mass n  Separate/confluent lymphadenopathy or large mass

displacing adjacent structures. No calcification before treatment

n  Role of PET CT > CT / MRI except for DWI MRI Mayerhoefer ME Clin Cancer Res 2014;20:2984-93

38 yo woman Hodgkin disease

20yo w NHL

Tumor of anterior mediastinum n  Thymus

n  Epithelial T n  Thymoma n  Carcinoma

n  Germ cell T n  Lymphoma n  Thymic Carcinoid n  Thymolipoma n  Cysts

n  other n  Para thyroid

Adenoma n  Lymphangioma n  Endothoracic Goiter

OMS 2004

Conclusion n  New anatomic classification n  Role of CT

n  Fat within tumor ? n  Cyts vs. cystic tumors n  Surgical vs. non surgical tumors

n  Role of biology n  Choice of appropriate biopsy technique