대한흉부영상의학회 Weekly Chest Cases

Case No : 908 Date 2015-03-23

Courtesy of Min Jae Cha, Myung Jin Chung / Samsung Medical Center
Age/Sex 48 / M
Chief ComplaintAbnormality on routine health check up.

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Contrast enhanced chest CT

Diagnosis With Brief Discussion

Diagnosis: Cystic thymoma
Radiologic Findings: Axial contrast-enhanced chest CT demonstrated a well-defined ovoid cystic mass in the left anterior mediastinum with an enhancing mural solid component.
On MRI, the mass exhibited high-signal intensity and the mural solid component within the mass exhibited intermediate to low-signal intensity on T2-weighted sequence with fat saturation. After contrast administration, the solid component showed enhancement. On axial diffusion weighted MR images obtained using a b value of 700 sec/mm2, both the cystic and solid components of the mass showed areas of high-signal intensity. However, the ADC value of the solid component was low (dark on the ADC map), suggesting diffusion-restriction.
Mediastinal mass excision was performed and pathology revealed cystic thymoma, WHO type B1.
Brief Review: Cystic thymoma is a variant of thymoma, characterized by a predominantly cystic component with an associated mural solid component. Although cystic lesions have been reported to be present in up to 40% of thymomas, those that are nearly entirely cystic are very rare. Cystic thymoma is mostly fluid owing to internal necrosis and cystic degeneration, and is often associated with solid intramural nodules. Foci of hemorrhage may also be present. It is a variant that was not accounted for by the 2004 WHO classification of thymic epithelial tumors.
CT can provide information on the precise anatomical location of this lesion as well as its relationship with surrounding structures in addition to its attenuation characteristics. Cystic thymomas appear as solitary round or ovoid masses with smooth or lobulated margins containing a large fluid component in the anterior mediastinum. On MRI, cystic changes and intratumoral necrosis manifest as areas of low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. To the contrary, fibrous septa within the tumor and associated nodularity can be seen as low-signal-intensity areas showing enhancement after contrast administration. Diffusion-weighted imaging (DWI) can also help evaluate the tissue composition in mediastinal masses as the nodular soft tissue component shows persistent high signal intensity on high-b-value DWI and a low ADC value, suggesting a lower chance of it being a true cyst.
Differential Diagnoses include cystic germ cell tumor, cystic lymphoma, cystic teratoma, cystic lymphangioma, and congenital cysts such as bronchogenic or pericardial cysts. The location of the mass and information obtained from CT and MRI can be of great help in terms of mass characterization.
References: 1. Beneviste MFK, Rosado-de-Christenson ML, Sabloff BS, et al: Role of imaging in the diagnosis, staging, and treatment of thymoma. RadioGraphics 31:1847-1861, 2011
2. Raad RA, Suh J, Ko JP. Case of the season: cystic thymoma. Semin Roentgenol. 2013;48(4):290–94.
3. Shin KE, Yi CA, Kim TS, et al: Diffusion-weighted MRI for distinguishing non-neoplastic cysts from solid masses in the mediastinum: problem-solving in mediastinal masses of indeterminate internal characteristics on CT. Eur Radiol. 2014 Mar;24(3):677-84.
Keywords: Mediastinum, Benign tumor,

No. of Applicants : 91

▶ Correct Answer : 48/91, 52.7%

- The University of Tokyo Hospital , Japan Akifumi Hagiwara
- Bahcesehir University School of Medicine, Radiology Department , Turkey Mustafa Kemal Demir
- Daejin Medical Center Bundang Jesaeng General Hospital , Korea (South) Donghwan Kim
- Seoul university hospital , Korea (South) Youngjin Ryu
- santosh hospital , India Pravin Mahadevappa
- Seirei Hamamatsu General Hospital , Japan Kenichi Mizuki
- �stanbul , Turkey Ayhan Yilmaz
- Diskapi Yildirim Beyazit Hospital, Ankara , Turkey Meric Tuzun
- University of British Columbia , Canada Amr Ajlan
- Osaka Rosai Hospital , Japan Hiromitsu Sumikawa
- Isfahan University Of Medical Sciences , Iran johary s
- UZA , Belgium Eline De Smet
- SQUH , Oman Saleh Baawain
- McGill University Health Center , Canada Alexandre Semionov
- Seoul National University Hospital , Korea (South) Hyoung-In Choi
- Okinawa Kyodo Hospital , Japan Shoko Iraha
- KAMC , Saudi Arabia Nesreen Abourokbah
- CHRU Lille , France Julien Pagniez
- SGPGIMS , India DEVINDER PAL DHANOTA
- CHU Poitiers , France Yannick DE LA TORRE
- GHICL , France manuel toledano
- CNUH , Korea (South) Noh Hoon
- chungbuk national university hospital , Korea (South) SOO JUNG LEE
- Dong-A University Hospital , Korea (South) Won Jin Choi
- Yokohama-asahi-chuo-general hospital , Japan Kyoko Nagai
- Asan Medical Center, Ulsan University , Korea (South) Mi Young Kim
- Asan Medical Center , Korea (South) Dong Wook Kim
- Asan Medical Center , Korea (South) Soyeoun Lim
- Asan Medical Center , Korea (South) , Korea (South) Han Na Lee
- Asan Medical Center , Korea (South) Hyung Jung Koo
- ACE DIAGNOSTICS , India DAMANDEEP CHAWLA
- SNUH , Korea (South) YE RA CHOI
- , Korea (South) Chan Park
- Ajou University hospital , Korea (South) Hun Cho
- Kizawa Memorial Hospital , Japan Yo Kaneko
- Pneumologia Universitaria, Policlinico di Bari , Italy Mario Damiani
- Shiga University of Medical Science , Japan Akitoshi Inoue
- chungbuk university hospital , Korea (South) Hyeonmi Ryu
- 異⑸ , Korea (South) Yunhee Jang
- PNUH , Korea (South) Seungbaek Hong
- pusan national university hospital , Korea (South) kim jeongmyeong
- IRSA La Rochelle , France Denis Chabassiere
- 異⑸ , Korea (South) Junghwan Kim
- Pusan national university hostpital , Korea (South) hyunjung kang
- Onomichi municipal hospital , Japan Hirofumi Mifune
- 媛 , Korea (South) Jo Yeseul
- CNUH , Korea (South) HYO JAE LEE
- ZIGONG TCM HOSPITAL OF CHINA , China Cao Cunyou

▶ Correct Answer as Differential Diagnosis : 25/91, 27.5%

- radiologist, aditya imaging centre , India vivek patel
- Oita University, Faculty of Medicine , Japan Fumito Okada
- DAYA General Hospital,Thrissur,Kerala , India Raveendran TK
- Kyoto University , Japan Akihiko Sakata
- Nagasaki University Hospital, Department of Pathology , Japan TOMONORI TANAKA
- SNUH , Korea (South) Eui Jin Hwang
- jaslok hospital & research centre mumbai , India JAINENDRA JAIN
- The University of Tokyo Hospital , Japan Toshihiro Furuta
- Niigata City General Hospital , Japan Takao Kiguchi
- MBAL BURGAS , Bulgaria VLADISLAV RUSINOV
- chp st martin , France Mariotte benoit
- CLCC Rennes , France nicolas gautier
- The University of Tokyo Hospital , Japan Takeyuki Watadani
- The University of Tokyo , Japan Eisuke Shibata
- Pusan national university hospital , Korea (South) hie bum suh
- National Center hospital of Neurology and Psychiatry , Japan Kaoru Sumida
- 遺 , Korea (South) LEE YOU JIN
- All India Institute of medical sciences , India Justin Moses
- Pusan national university of hospital , Korea (South) Jo ji eun
- Fortis hospital , Mohali , India Shaleen Rana
- CLINIQUE STE CLOTILDE , Reunion patrick MASCAREL
- Okayama University Hospital , Japan Toshiyuki Komaki
- Onomichi Municipal Hospital , Japan Yoshihisa Masaoka
- VHS medical center , Korea (South) Keuntak Roh
- Pusan national university hospital , Korea (South) So Park

▶ Semi-Correct Answer : 4/91, 4.4%

- James Paget Hospital , U.K , United Kingdom nabil mahmood
- Deptt of Radiodiagnosis & Imaging, PGIMER chandigarh , India Ram Galwa
- Pusan National University Yangan Hospital , Korea (South) yoonyoung choi
- Northern Yokohama Showa university , Japan Kota Watanabe

대한흉부영상의학회 Korean Society of Thoracic Radiology

Archive of Old Cases

Case No : 908 Date 2015-03-23

Discussion

No. of Applicants : 91