Exploring the Histogenesis and Diagnostic Strategy Using Immunoassay and RT-PCR in Alveolar Soft Part Sarcoma

Alveolar soft part sarcoma (ASPS) is a rare soft tissue sarcoma, but it's easily misdiagnosed in rare locations. The derivation of ASPS is still uncertain, therefore we conducted this study to explore the histogenesis of ASPS by analyzing stem cell markers (ALDH1, CD29, CD133 and Nestin). Protein TFE3 and fusion gene ASPS-TFE3 were tested in paraffin to explore diagnostic strategy and molecular pathological features. In this study, nine cases of ASPS were immunostained with stem cell surface markers (ALDH1, CD29, CD133 and Nestin) and protein TFE3. Seven cases of ASPS mRNA were successfully extracted from nine paraffin-embedded tissues. The expression of fusion gene ASPL-TFE3 was examined by reverse transcriptase-polymerase chain reaction. The immunohistochemical staining of nine patients showed that CD29 and Nestin were negative in all nine cases (0/9). CD133 was weakly positive in one cases (1/9) and ALDH1 was weakly positive in one cases (1/9). TFE3 was positive in nine cases (9/9). Seven paraffin tissues could be successfully extracted with mRNA in nine cases. The results of Reverse Transcription Polymerase Chain Reaction (RT-PCR) showed that ASPL-TFE3 fusion transcripts could be tested in the seven cases (four cases being type 2 and three cases being type 1). The positive rate of CD133 and ALDH1 were less than 1% and the expression of CD29 and Nestin were negative in ASPS. Immunohistochemistry results indicated that the histogenesis of ASPS maybe not derive from mesenchymal stem cells. Immunohistochemistry staining showed that TFE3 protein expression was highly sensitive in ASPS. Furthermore, RT-PCR results showed that fusion gene ASPL-TFE3 (ASPL-TFE3 type 1 and ASPL-TFE3 type 2) was expressed in ASPS, which could provide information for clinical molecular pathological diagnosis and improve the diagnosis rate of rare atypical ASPS.