PMC9798226_01
The timeline showed the clinicopathological process.
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The timeline is summarized in  Figure 1 .
Histologic and immunohistochemical features. (A) Histological examination revealed a relatively well-defined, nodular tumor without capsule (H&E, low magnification). (B) Monomorphic spindle cell tumor composed of cellular fascicles of bland fibroblasts with hyalinization and mucoid degeneration (H&E, medium magnification). (C) Spindle cells showed elongated nuclei with finely dispersed chromatin and small inconspicuous nucleoli (H&E, high magnification). (D) Tumor cells showed diffuse nuclear staining for ERG (medium magnification).
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Histological examination revealed a relatively well-defined and nodular tumor without a capsule ( Figure 2A ). The tumor cells had pale eosinophilic cytoplasm and elongated nuclei with finely dispersed chromatin and small inconspicuous nucleoli ( Figures 2B, C ). By immunohistochemistry, the spindle tumor cells showed diffusely and strongly nuclear positive for ERG ( Figure 2D ), while S100, alpha-SMA, CD34, desmin, SATB2, EMA, MUC4, and other spindle cell tumor and vascular markers were negative.
Molecular detection. (A) FISH assay showed an unbalanced rearrangement of EWSR1 with loss of the telomeric part (green). (B) FISH assay showed EWSR1 (green) and SMAD3 (red) fusion signal (yellow). (C) RT-PCR identified exon 7 of EWSR1 and exon 6 of SMAD3 gene fusion. FISH, fluorescence in situ hybridization.
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The FISH assessment demonstrated an unbalanced rearrangement of EWSR1 with loss of the telomeric part ( Figure 3A ), combined with tumor cells, diffuse nuclear staining for ERG the diagnosis of EWSR1::SMAD3-rearranged fibroblastic tumor was considered. To identify the fusion partner, EWSR1 and SMAD3 fusion was detected by FISH ( Figure 3B ), and the fusion was confirmed by RT-PCR and Sanger sequencing between exon 7 of EWSR1 and exon 6 of SMAD3 ( Figure 3C ).