A serologic test to determine levels for CA-125, an antigen that was thought to mark nonmucinous epithelial ovarian carcinomas, was first described in 1983.1 Since then, the use of CA-125 in the monitoring of epithelial ovarian cancers has been well documented.2 However, it has been equally well defined that elevated CA-125 levels are not specific for ovarian cancers but can be found in other malignancies, including those of the pancreas, breast, colon, and lung.2 Furthermore, increased CA-125 levels can also be found in benign conditions, particularly in those associated with serosal fluid accumulation (ascites and pleural and pericardial effusion).3 The case we recently presented of a woman with MCTD4 and elevated CA-125 levels highlighted yet another potential diagnostic pitfall with the use of this antigen as a malignancy marker.
Kwong YL, Au WY. Cancer Antigen 125: Tumor or Serosal Marker in Case of Ascites?—Reply. Arch Intern Med. 2001;161(20):2508. doi: