Clinical significance of an inconclusive cytopathologic diagnosis. I. Positive predictive value

We retrospectively analyzed the pathology database of 1,057 patients at Duke University Medical Center who received an inconclusive cytopathologic diagnosis during the five-year period 1984-1989 in an attempt to answer the question, what is the significance of a cytopathologic diagnosis of "atypical cells are present that are suspicious for, but not diagnostic of, malignancy?" We identified 1,110 cytologic specimens from all body sites receiving this diagnosis, and of them, 805 (73%) had a follow-up specimen from the same anatomic site that was definitive as to the presence or absence of malignancy; 305 (27%) had no follow-up specimen. Of the follow-up specimens, 596 (74%) were histopathologic specimens, and 209 (26%) were cytopathologic. Specimens from the respiratory tract accounted for 51% (563) of the cases, and the positive predictive value (PPV) of an inconclusive diagnosis at this site was 85%. Of the remaining specimens, those from the urinary (10%) and genital (8%) tracts were the most common, and the PPVs of an inconclusive diagnosis at these sites were 83% and 61%, respectively. The overall PPV of an inconclusive cytologic diagnosis from all body sites was 80% and ranged between 57% and 93%, depending on the anatomic site.