ALDH1A1 belongs to the ALDH enzymes, a family of evolutionarily conserved enzymes comprised of 19 isoforms that are localized in the cytoplasm, mitochondria or nucleus. ALDH1A1 is predominantly expressed in the epithelium of testis, brain, eye, liver, kidney, as well as neural and hematopoietic stem cells. Recently, it has been reported that high ALDH1A1 mRNA expression was seen in solitary fibrous tumor (SFT) and hemangiopericytoma (HPC), compared to meningiomas and synovial sarcomas. Anti-ALDH1A1 can be combined with anti-CD34 to aid in the differentiation between SFT, HPC, meningioma, and synovial sarcoma.