p53 in Endometriosis

To the Editor: I read with interest the recent article by Nakayama et al. describing focal p53 expression in endometriotic lesions (1). I have occasionally observed endogenous biotin expression in endometriotic lesions (personal observation) in a pattern very similar to that illustrated in Figure 2 of the article (isolated cells with intense nuclear staining). Although the Materials and Methods section did not mention negative controls, I presume these were done. Negative controls should be reviewed to rule out the possibility of false positive staining due to endogenous biotin. Khush Mittal, M.D.