Value of the filter imprint technique in aspiration biopsy cytology.

In 468 fine needle aspiration (FNA) biopsies, after smearing of the aspirate on glass slides, additional material was obtained by flushing the needle with a fixative. The cells were collected on Millipore filters, from which imprints were prepared. The filter imprints were found to be sufficiently cellular in 60% of the cases, which reduced by 33 (7.3%) the number of cases with unsatisfactory aspirates. Diagnostic specificity and sensitivity were not influenced by the technique. The filter imprint technique was of particular value in breast aspirates.