Comparison of flow cytometric data obtained using fresh and paraffin-embedded lymphoid tissue

Flow cytometric (FCM) DNA analysis was carried out on 24 lymph nodes: 13 from benign reactive hyperplasias and 11 from non-Hodgkin's lymphomas. FCM was performed on two types of samples: (1) fresh cell suspensions and (2) suspensions prepared from formalin-fixed, paraffin-embedded sections. FCM of fresh samples detected aneuploidy in 23 of the 24 cases while FCM of paraffin-embedded samples detected aneuploidy in only 6 of the 24 cases. Those six cases were lymphomas considered histologically as having a poor prognosis. Only one case, a lymphoma, was euploid with both methods. The coefficients of variance determined in each case for both methods were found to be within "normal ranges," but were greater in the paraffin-embedded specimens. The results suggest that FCM DNA analysis of formalin-fixed, paraffin-embedded sections does not have as great a resolution capacity as does analysis of fresh cell suspensions, since the former failed to detect cell populations that had a small degree of aneuploidy (close to the 2n population).