Analysis of false positive and false negative endometrial cytology through rescreening and reexamination

Among the 2346 endometrial cytodiagnostic studies performed at Kure Kyosai Hospital from 1987 to 1990, there were 7 false positives (0.3%) and 5 false negatives (0.2%). These misdiagnosed specimens were rescreened by 16 certified cytotechnologists at other hospitals and reexamined. Of the 7 false-positive cases among the 44 positive cases, 4 were ultimately diagnosed as atrophic endometrium, 1 as IUD endometrium, 1 as syncytial endometritis, and 1 as normal endometrium. There were 19 cases of endometrial carcinoma, 5 of which were judged negative, 3 suspicious, 9 positive, and 2 inadequate. Among the 5 false-negative cases, 4 were welldifferentiated endometrial adenocarcinoma and 1 was adenoacanthoma. As a result of rescreening, the cases of atrophic endometrium were judged positive by 21% of the cytotechnologists, the IUD case as positive by 13%, the syncytial endometritis as positive by 7%, the degenerated normal endometrium as positive by 50%, the well-differentiated adenocarcinoma as negative by 44%, and the adenoacanthoma as negative by 81%. The length of time the cytotechnologists had been certified had no effect on their decisions except in the case of atrophic endometrium. Reexamination of cytology and histology revealed that the false diagnosis was caused by atypical cells resembling regenerative epithelium in the cases of atrophic endometrium and syncytial endometritis, by poor cytological criteria and no information in the IUD case, by the presence of degenerative cells in the case of normal endometrium and by a sampling error in the case of adenoacanthoma. Diagnosis was difficult in some cases of atrophic endometrium and welldifferentiated adenocarcinoma.