Significance of immunohistochemistry and FISH of TFE3 in the diagnosis of alveolar soft part sarcoma: A case report

Rationale: Alveolar soft part sarcoma (ASPS) is a rare soft tissue sarcoma harboring an ASPL-TFE3 fusion gene. Herein, we report a case of ASPS associated with brain metastasis. Immunohistochemistry (IHC) for TFE3 antigen expression and fluorescence in situ hybridization (FISH) for TFE3 rearrangement were performed to arrive at an accurate diagnosis. Patient concerns: A 47-year-old man was hospitalized for a headache and numbness of the lower limbs. Diagnoses: Preoperative computed tomography and magnetic resonance imaging revealed 2 brain masses, 1 each in the right parietal and temporal bones. We diagnosed this case as ASPS with brain metastasis based on histological morphology, IHC, and FISH. Interventions: The patient underwent right skull titanium mesh implantation and supratentorial superficial lesion resection. Outcomes : The patient recovered well after discharged from hospital. Lessons: The diagnosis of ASPS depends on careful clinical, radiographic, histopathological, IHC, and FISH assessments to arrive at the correct diagnosis. Thus, TFE3 may be useful in the diagnosis and treatment of ASPS.