Update, 11 a.m.: The Washington Post's David Weigel asked Carson about the paper at a Thursday campaign stop in New Hampshire; you can read about his response here. The long and short of it is that Carson stood by his criticism of Planned Parenthood but said somewhat contradictorily that he doesn't think that fetal tissue research is immoral or should be banned.
Original post, 10:45 a.m.: Retired neurosurgeon Ben Carson, who's done well in some recent Republican 2016 primary polls, has been very critical of Planned Parenthood since the release of "sting" videos that document its donation of fetal tissue to medical researchers. From Breitbart:
Carson said, in response, to the argument that Planned Parenthood uses fetal organs for medical research, “it’s been over-promised what the benefits of fetal research would be. And very much under-delivered. And if you go back over the years, and look at the research that has been done and all the things that it was supposed to deliver, very little of that has been done, and there’s nothing that can’t be done without fetal tissue."
Many defenders of Planned Parenthood's activities have indeed cited the medical usefulness of fetal tissue research—and it turns out that Carson himself has actually conducted such research. A writer and doctor named Jen Gunter found the evidence:
While opining on the uselessness of fetal tissue research to Megyn Kelly Dr. Carson neglected to mention his own paper Colloid Cysts of the Third Ventricle: Immunohistochemical evidence for nonneuropithelial differentiation published in Hum Pathol 23:811-816 in 1992. The materials and methods describe using “human choroid plexus ependyma and nasal mucosa from two fetuses aborted in the ninth and 17th week of gestation.”
Carson, who published the paper with three other doctors, hasn't commented yet on the seeming contradiction.