Intraspinal ASPSCR1::TFE3 rearranged tumor with nerve differentiation.

The ASPSCR1::TFE3 rearrangement has been described in alveolar soft part sarcoma, MiT family translocation renal cell carcinomas as well as perivascular epithelioid cell tumors (PEComas). However, this rearrangement has not been reported in the primary spinal canal. Here, we report a case of an 18-year-old male who had pain in his left lower limb for 2 months. Neuroimaging revealed a lesion in the spinal canal from thoracic 12 to lumbar 1. Histopathological examination showed the tumor consisting of nested architectural pattern with abundant psammomatous calcification. Tumor cells exhibited strong and diffuse positivity for TFE3 and SOX10, patchy positivity for HMB-45 and S100, while other immunomarkers were negatively stained. RNA sequencing confirmed the ASPSCR1::TFE3 gene rearrangement. The Heidelberg DNA methylation classifier classified this case as "Cranial and Paraspinal Nerve Tumor". This case may represent a novel intraspinal neoplasm entity that expands the spectrum of ASPSCR1::TFE3-rearranged neoplasms by unique histopathological features and potential neural differentiation. We named this case as intraspinal ASPSCR1::TFE3 rearranged tumor with SOX10 expression.