The cell block for body cavity fluids: do the results justify the cost?

We reviewed retrospectively reports on cytologic smears and cell blocks from body cavity fluids received in our department over a 12-mo period. In order to evaluate the usefulness of the two modalities independently, all available slides were studied with the reviewers blinded to the original diagnoses, history, and appearances on corresponding cytology/cell block. Of 524 cytology samples, 283 had cell blocks, of which 263 were available for comparative cytologic and histologic review. Twenty-four cases based on the original reports and 22 cases in the review had diagnoses with major discrepancies between the cell block and cytology. On original reports, cytology favored malignancy in 21 cases in which the cell block was benign, with one false suspicious cytology. In three cases, the cell block was suspicious/positive (two false suspicious cell blocks), but cytology was negative/atypical. In the review diagnoses, there were also 21 cases of suspicious/positive cytology (one false suspicious cytology) and negative/atypical cell blocks. In only one case did the cell block favor malignancy when cytology was benign (a false suspicious cell block). Review of Medicare data indicated that the physician's fee charged for these 283 cell blocks would range from about $7,000 to $28,000 to detect one additional malignancy. We conclude that the routine use of cell blocks is not a cost-effective method of detecting malignancy in body cavity fluids. We advise that samples be refrigerated or be kept fixed. If immunoperoxidase studies are desired following cytologic evaluation, they may be performed subsequently on fresh smears or a cell block.