PMC8440875_01
(A) Computed tomography showed an occupying lesion involving the right atrium and the right ventricle. (B) Echocardiography revealed a mass in the right atrium with moderate pericardial effusion.
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F1
A computed tomography (CT) scan showed an occupying lesion involving the right atrium and the right ventricle (Figure 1A) without any abdominal abnormalities. The echocardiography revealed a mass in the right atrium with moderate pericardial effusion (Figure 1B).
Histological findings and immunohistochemical staining of the cardiac lesion. (A) The neoplastic cells proliferated diffusely in the pattern of nests and sheets with scattered deposition of pigment (x100). (B) Fibrous separation was notable (x100). (C) Focal areas with remarkable cellular dyscohesion imparted a vague pseudopapillary pattern (x100). (D) The tumor cells were small to medium in size with fine chromatin and predominantly pale eosinophilic cytoplasm. The nuclei were typically round to oval with somewhat irregular contours and contained small nucleoli. Cytoplasmic clearing was also observed. The mitotic figures were easily found (x400). The tumor cells were strongly and diffusely positive for (E) S100 and (F) SOX10 (x100), (G) moderately positive for Syn, and (H) negative for HMB45.
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F2
Microscopically, neoplastic cells proliferated diffusely in the pattern of nests and sheets with fibrous separation (Figures 2A,B). Focal areas with remarkable cellular dyscohesion imparted a vague pseudopapillary pattern (Figure 2C). The nuclei were typically round to oval with somewhat irregular contours and contained small nucleoli (Figure 2D). Cytoplasmic clearing was also observed in this case, while osteoclast-like multinucleated giant cells were not identified (Figure 2D). In addition, deposition of hemosiderin was found as proved by iron staining (Figure 2A). Immunohistochemically, the neoplastic cells were strongly and diffusely positive for S100 (Figure 2E) and SOX-10 (Figure 2F) and moderately positive for Syn (Figure 2G), while they were negative for HMB45 (Figure 2H), A103, and CD99.
Molecular characteristics of the lesion. (A) The rearrangement of EWSR1 (arrows) was found in about 50% of tumor cells by fluorescence in situ hybridization using EWSR1 break-apart probe. (B)
EWSR1-AFTF1 dichromatic fusion probe also proved the tumor carrying the EWSR1 rearrangement (arrows). (C) Whole-transcriptome sequencing analysis confirmed that the fusion involved exon 8 of EWSR1 and exon 4 of ATF1.
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F3
Fluorescence in situ hybridization (FISH) preformed on paraffin-embedded mass tissues identified EWSR1-ATF1 rearrangement by EWSR1 break-apart probe (Figure 3A) and EWSR1-ATF1 dichromatic fusion probe (Figure 3B), respectively. Furthermore, the whole-transcriptome sequencing analysis confirmed that this fusion involved exon 8 of EWSR1 and exon 4 of ATF1 (Figure 3C).
Timeline of this study.
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F4
The timeline is shown in Figure 4.