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(a) Unenhanced and (b) contrast-enhanced images of initial chest computed tomography. There is a 9 x 7 cm mass (arrows, a,b) in the anterior mediastinum, which had a lobular margin and showed heterogeneous enhancement without a demonstrable fat component, with extrinsic compression and/or early invasion of adjacent mediastinal great vessels and left upper lobe. aA, ascending thoracic aorta; dA, descending thoracic aorta; rMP, right main pulmonary artery.
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The initial contrast-enhanced chest computed tomography (CT) images revealed a 9 x 7 cm mass in the anterior mediastinum showing heterogeneous enhancement (Fig 1).
Microscopic findings of malignant teratoma in (a-c) first transthoracic needle biopsy (TTNB) and liposarcoma in (d-e) second TTNB. The tumor (a) had teratomatous features (hematoxylin-eosin [HE], original magnification x40), and showed (b) immature neuroepithelial components (HE, original magnification x200), (c) an immature cartilage component (HE, original magnification X200), and (d) several lipogenic tissues with dense collagenous tissue (HE, original magnification x40). (e) The fat cells showed immunoreactivity for MDM2 (original magnification x200).
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Based on laboratory test results and imaging findings suggesting an invasive anterior mediastinal tumor, we presumed that the mass was a primary non-seminomatous malignant GCT and transthoracic needle biopsy (TTNB) confirmed that the specimen was teratoma with suspicious immaturity (Fig 2a-c).3  TTNB, which targeted the growing fat component. This specimen pathologically revealed a well-differentiated liposarcoma (Fig 2d-e).
Double inversion-recovery (IR) (a) T1 weighted, (b) T2-weighted, and (c) gadolinium-enhanced T1 weighted chest magnetic resonance imaging at one month follow-up. A huge, prominent heterogeneous anterior mediastinal mass (arrows, a-c) contains a relatively large hemorrhagic and necrotic portion, which shows subtle high signal intensity on T1 weighted image (asterisk, a), a heterogeneous mixed area of strong high and dark signal intensities on T2 weighted imaging (asterisk, b), and low signal intensity without contrast enhancement on contrast-enhanced T1 weighted image (asterisk, c). (c) The remaining portion of the mass shows heterogeneous enhancement, which is suggestive of malignant potential. aA, ascending thoracic aorta; dA, descending thoracic aorta; rMP, right main pulmonary artery.
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However, a follow-up CT series taken one month later showed that the tumor had markedly increased in size (data not shown) and contrast-enhanced magnetic resonance imaging revealed a huge heterogeneous anterior mediastinal mass with marked interval growth (Fig 3).
Follow-up contrast-enhanced computed tomography (CT) imaging at three months. The anterior mediastinal mass (arrows) also shows marked interval growth and heterogeneous enhancement with a marked hypervascular portion (asterisk). Also the fat component within the tumor (arrowhead), which was not clear on baseline CT, is clearly demonstrated.
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The fat component within the tumor, which was not clear on baseline CT, was clearly demonstrated on follow-up contrast-enhanced CT images at three months (Fig 4).