PMC10226891_01
MRI and CT-scan. (A) Post-contrast T1 vibe (volumetric interpolated breath-hold examination) fat saturated sagittal MR-image, depicting a supra-cardial fatty mass (indicated by arrows). (B) Contrast-enhanced transverse CT-image showing the left para-cardial located low density mass (indicated by arrows). MRI, magnetic resonance imaging; CT, computed tomography; MR, magnetic resonance.
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The magnetic resonance imaging (MRI)-scan (Figure 1A) and computed tomography (CT)-scan (Figure 1B) showed a hypointense (MRI)/hypodense (CT) tumour with focally more intense (MRI)/denser (CT) areas in the anterior mediastinum, abutting the aortic arch, pulmonary trunk and left ventricle.
Gross image of resected tumour. (A) Thinly encapsulated 12.5 cm excised tumour. (B) On sectioning a predominantly fatty specimen is seen with focally grey fibrous areas.
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A thinly encapsulated soft tumour of 12.5x8.0x2.5 cm weighing 153 g was received (Figure 2A), which on sectioning mainly consisted of pale yellow fatty tissue with areas of pink-grey fibrous tissue (Figure 2B).
Histology. (A) Fibro-fatty tissue with ramifying cords of epithelial cells. Mature fatty tissue, present in several areas in this slide (a single area indicated by *). Pink fibrous collagenous tissue is indicated (#). Darker branching strands of epithelial cells ramify through both fibrous and fatty tissue. (B) Scattered small calcifications were present, again note the slender strands of epithelial cells. (C) Discrete collections of spindled epithelial cells, comparable to those of a spindle cell thymoma. (D) Lymphoid component with a Hassall's corpuscle. HE stained sections (A,B: low power view; C,D: medium power view). HE, hematoxylin-eosin.
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A tumour with multiple components was seen in microscopy (Figure 3A-3D), areas of mature fat were admixed with pauci-cellular connective tissue with scattered collections of small lymphocytes. The proportion of fatty tissue to collagenous connective tissue varied considerably within the tumour (Figure 3A). Throughout these components branching interconnected cords of small epithelial cells were present (Figure 3B), occasionally associated with small solid collections of non-atypical spindled cells (Figure 3C). Scattered Hassall's corpuscles were present (Figure 3D), typically located within lymphoid aggregates.
Immunohistochemistry. The epithelial strands are highlighted in the AE1/AE3 cytokeratin (A) and p63 (B) stains (medium power views). The lymphoid component shows a mixed B-cell (CD20 positive) population (C) combined with an immature (TdT positive) T-cell population (D) (medium power views).
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The strands and small foci of spindled cells stained for cytokeratin (pan-cytokeratin AE1-AE3) and p63 (Figure 4A,4B). The lymphoid aggregates were mainly composed of immature T-cells (CD3/TdT positive) often with small collections of CD20 positive B-cells (Figure 4C,4D).