The accuracy of fine needle aspiration biopsy for flow cytometric determination of tumor DNA content

The use of fine needle aspiration (FNA) to obtain a diagnosis of malignancy is established in the practice of oncology, but there is little information on its accuracy in sampling tumor DNA content. We therefore compared flow cytometric DNA data obtained from FNA-derived samples with that obtained after digestion of the same murine tumor from which the aspirates had been taken. Fifteen female C3Hf/Kam mice were implanted with MCA-29 tumor cells from the same source tumor. MCA-29 is a multiploid mammary adenocarcinoma with two aneuploid populations (DNA Index of A = 1.67, B = 1.89). The tumors were grown to a mean size of 8.6 mm. After sacrifice, three FNAs were performed on each tumor, following which the whole tumor (WT) was excised and homogenized. All FNA and WT samples were digested with 0.04% pepsin and the nuclei stained with propidium iodide in preparation for flow cytometry. DNA histograms of the aspirates were compared with the corresponding WT histograms. Any single FNA detected population A in all (100%) cases and detected the less prominent population B in 94.3% of instances. Any single FNA was able to detect the same populations that were present in the whole tumor in 95.4% of cases, while the set of three aspirates matched the corresponding WT in 100% of cases. We conclude that FNA DNA histograms are accurate for the assessment of ploidy, but that in order to ensure detection of all tumor populations present, multiple aspirates are needed.