PMC10404896_01
Examination of the pleural effusion showed massive lymphocytes, and no obvious heterotypic epithelial cells were detected.
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The patient underwent transcatheter thoracic drainage to determine the features of the pleural effusion, and a routine examination showed bloody turbid pleural effusion without tumor cells (Figure 1).
CT scan of the thorax. (a and b) A mass with multiple small vessel shadows was observed near the mediastinum. A pleural effusion was found in the left thorax. (c and d) Chest CT after one cycle of chemotherapy showed that the mass and fluid decreased. (e and f) After six treatment cycles, the tumor was hard to observe, and no pleural effusion could be observed. CT: computed tomography.
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A chest computed tomography (CT) scan showed a large soft tissue mass (15.7 x 11.7 x 10.5 cm) near the left mediastinum with multiple nodules and masses in the left pleura, and the fluid could be seen on the same side of the thorax (Figure 2a and b). Moderately heterogeneous enhancement with multiple small vessel shadows could be seen in the aforementioned mass and nodules after the injection of a contrast agent (Figure 2a and b). After finishing one cycle of chemotherapy, a CT scan of the chest revealed that the tumor was approximately half its size before treatment, and the pleural effusion had decreased (Figure 2c and d). After six cycles of treatment, the tumor was hard to observe, and no pleural effusion was observed (Figure 2e and f).
Pathological examination of the tumor. (a) Hematoxylin and eosin staining of the mass showed small and deeply stained cells with less extracellular matrix. (b-d) Immunohistochemistry of sections showed positivity for CD99, FLI-1, and NKX2. Scale bar = 20 mum.
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The tumor cells were negative for MPO, GFAP, CD30, EMA, CgA, desmin, and WT-1 (Figure 3).
Molecular pathology of the tumor was detected by FISH. (a and b) Molecular pathology indicated EWSR1 rearrangement. The percentage of cells with EWSR1 breakage (red and green signal points separated) in the visual field was approximately 71%.
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Fluorescence in situ hybridization (FISH) suggested EWSR1 gene breakage and rearrangement (Figure 4).