Nonreportable Cell-Free DNA Prenatal Screening Test Leads to Colorectal Cancer Diagnosis in the Mother

Cell-free DNA, DNA from the developing placenta, is a noninvasive prenatal screening test to detect common fetal chromosomal abnormalities. Rarely, nonreportable results occur when the test cannot accurately determine the fetus chromosomal status. This can be due to low fetal fraction, insufficient DNA, or multiple aneuploidies, which can suggest maternal malignancy. Workup of occult malignancy in pregnancy is challenging. Most malignancies reported to date have been lymphomas. We describe the case of a pregnant patient without cancer risk factors who, following a nonreportable Cell-free DNA test, presented with abdominal pain and intermittent blood per rectum and was ultimately diagnosed with metastatic colon cancer.