Specialties: Soft Tissue Pathology

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.¹ ALDH1A1 is predominantly expressed in the epithelium of testis, brain, eye, liver, kidney, as well as neural and hematopoietic stem cells.² 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.³ An immunohistochemical study with ALDH1 A1 antibody in 243 meningeal tumors (tissue microarray), including 25 central nervous system SFTs, 13 extrameningeal SFTs, 55 central nervous system HPCs, 163 meningiomas, and 98 synovial sarcomas³ found that 21 of 25 meningeal SFTs (84%), 11 of 13 extrameningeal SFTs (84.6%), and 18 of 24 (85.4%) meningeal HPCs were positive with anti-ALDH1A1 antibody. Anti-ALDH1A1 can be combined with anti-CD34 to aid in the differentiation between SFT, HPC, meningioma, and synovial sarcoma.³ 24/25 (96%) meningeal SFTs and 54/55 (98%) meningeal HPCs were positive for ALDH1A1 and/or CD34 whereas only 10/163 (6%) meningiomas and 7/98 (7%) synovial sarcomas were positive for ALDH1A1 and/or CD34.³ Anti-ALDH1A1 IHC has been recommended for routine use in association with anti-CD34 for the differentiation among SFT, HPC, meningioma, and synovial sarcoma.³