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Weekly Chest CasesArchive of Old Cases

Case No : 1394 Date 2024-07-10

  • Courtesy of Hyun-ju Lim, Kun Young Lim, Soo-Hyun Lee, Hyae Young Kim / National Cancer Center
  • Age/Sex 16 / M
  • Chief ComplaintAbnormal finding on check-up chest radiograph
  • Figure 1
  • Figure 2
  • Figure 3
  • Figure 4
  • Figure 5

Diagnosis With Brief Discussion

Diagnosis
Cystic thymoma
Radiologic Findings
Fig.1. Chest radiograph shows bulging opacity in left hilar area.

Fig. 2-3. Contrast-enhanced CT scan reveals cystic mass (10.4cm in diameter on coronal image) with internal enhancing nodular areas in the anterior mediastinum.

Fig. 4. 18F-FDG-PET CT scan shows hypermetabolism within the anterior mediastinal cystic lesion.

Fig.5. Mediastinal excision was performed. Macroscopic appearance of the resected tumor shows solid nodular components within the cystic space. Pathology revealed cystic thymoma, WHO type B1.
Brief Review
Thymomas are relatively uncommon anterior mediastinal tumors derived from thymic epithelium. Nearly all occur in patients over the age of 20 years, and 70% occur in patients over the age of 40 years. Thymomas in children and adolescents are exceedingly rare and because of their rarity, may be difficult to diagnose.
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.
On CT scans, cystic thymomas appear as solitary round or ovoid masses with smooth or lobulated margins containing a large fluid component in the anterior mediastinum. Differential diagnoses include cystic germ cell tumor, cystic lymphoma (mostly Hodgkin lymphoma), cystic teratoma, cystic lymphangioma, and congenital cysts such as bronchogenic or pericardial cysts.
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. On 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.
Although the majority of thymomas are encapsulated and slow growing, 10–15% are invasive. Therapy for thymoma is directed at complete surgical resection, with radiation and chemotherapy reserved for treatment of invasive and malignant disease. When tumors are encapsulated and completely resected, prognosis is excellent. However, in patients with invasive or metastatic disease, prognosis is poor.
References
Verhey P et al. AJR 2006;186:1176-1180
Raad R et al. Semin Roentgenol 2013;48:290-294
Keywords

No. of Applicants : 61

▶ Correct Answer : 1/61,  1.6%
  • - Juntendo University , Japan YUTAKA IKENOUCHI
▶ Correct Answer as Differential Diagnosis : 30/61,  49.2%
  • - Kyoto University , Japan AKIHIKO SAKATA
  • - Korea University Anam Hospital , Korea (South) KYU-CHONG LEE
  • - Other , Korea (South) DOWOO KIM
  • - Kyoto City Hospital , Japan YUSUKE UTSUNOMIYA
  • - Seoul National University Hospital , Korea (South) MEE SUN LEE
  • - , Sweden MOHAMAD TLASS
  • - The Catholic University of Korea Yoeuido St. Mary , Korea (South) CHAWOONG JEON
  • - The University of Tokyo Hospital , Japan TOSHIHIRO FURUTA
  • - Shiga General Hospital , Japan YUSAKU MORIBATA
  • - Osaka metropolitan university Hospital , Japan TATSUSHI OURA
  • - Jiangsu province hospital , China WANGJIAN ZHA
  • - Healthy Longevity Medical Center , Japan SHIN-ICHI CHO
  • - , Japan SUZUNE TSUKAMOTO
  • - medical scanning , Japan HIROAKI ARAKAWA
  • - Dokkyo Medical University , Japan HIROAKI ARAKAWA
  • - The University of Tokyo Hospital , Japan JUN KANZAWA
  • - Ome Medical Center , Japan MIKIYA FUJII
  • - Kyoto University , Japan SHO KOYASU
  • - , Korea (South) DONG-HO BANG
  • - , Japan SHUNJIRO NOGUCHI
  • - Fukuoka university , Japan KEISUKE SATO
  • - , India ANURAG PRATAP SINGH CHAUHAN
  • - GHICL , France MANUEL TOLEDANO
  • - Vita Hospital , Brazil DIOGO LAGO PINHEIRO
  • - Toyota Kosei Hospital , Japan YUKI HAYASHI
  • - Kantou Rousai Hospital , Japan KAORU SUMIDA
  • - Secomedic Hospital , Japan FUMINORI MIYOSHI
  • - Oita university , Japan AYUMI KAMEI
  • - Paras hospital, Panchkula , India SHALEEN RANA
  • - , Japan YOSHIKI ISHII
▶ Semi-Correct Answer : 8/61,  13.1%
  • - , Japan KENTARO KOTANI
  • - Saitama-Sekishinkai Hosptal , Japan MIHOKO YAMAZAKI
  • - University of Yamanashi , Japan TAKAAKI HASHIMOTO
  • - Other , Korea (South) SEONGSU KANG
  • - Osaka Metropolitan University Hospital , Japan SHU MATSUSHITA
  • - Shiga University of Medical Science , Japan AKITOSHI INOUE
  • - University of Yamanashi , Japan KOJIRO ONOHARA
  • - Jichi Medical University, School of Medicine , Japan MITSURU MATSUKI
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