Figure 2. Immunohistochemistry of ARID1A (BAF250A) in Deep Infiltrating Endometriosis.
ARID1A immunoreactivity was detected in all stromal (St) cells and epithelial (Epi) cells within an endometriotic lesion containing wild-type ARID1A (Panel A). In Patient 20, harboring an ARID1A inactivating mutation, loss of ARID1A immunoreactivity was observed in a subset of epithelial cells (arrows indicate examples), but immunoreactivity was preserved in a much larger fraction of the adjacent stromal cells within the same lesion (Panel B). The mutant-allele fraction of the ARID1A mutation in this patient was 8%.