False negatives and false positives in oral cytology


Makoto Suzuki 1,2) and Takashi Saku 1,2)
1) Surgical Pathology Laboratory, Niigata University Dental Hospital
(Chief: Prof. Takashi Saku)
2) Department of Pathology, Niigata University School of Dentistry
(Chief: Prof. Takashi Sake)


Summary: False negative and false positive oral cytology cases were re-screened in order to determine the causes of the diagnostic errors. False negatives were often based on insufficient sample-taking, or inadequate smearing such as crowding of cells, contamination by blood cells and drying of smears. Overlooking atypical cells, underestimation of atypical cytomorphology and mistaking carcinoma cells for normal mesenchymal cells were other factors of false negative diagnoses.
        False positives were mainly caused by misinterpretation of cell morphology, such as overestimation of cellular atypia, or mistaking the swollen non-epithelial cells for carcinoma cells. In order to minimize false diagnoses, refined technique of sample-taking and smearing, and improved ability in cytodiagnosis are essential. When specimens are inadequate to evaluate cytologically, because of poor preparation, diagnosis should be suspended and re-examination or excisional biopsy is to be indicated.
        It seems to be rational to establish a diagnostic system in which cytopathologists evaluate the quality of specimens prior to cell diagnosis.
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