DNA flow cytometry of primary tumors and their skin metastases: Correlation of DNA histograms

The purpose of this study was to determine whether quantification of DNA content would demonstrate conserved patterns in primary tumors and their metastases and to learn whether this technique would be useful in determining if a tumor was metastatic from a previous primary tumor or represented a new neoplasm. The study comprised of all cases nonmelanoma metastatic skin lesions in which the primary tumor was also resected at this hospital between the years 1984 and 1990 (22 cases). Both the primary and metastatic lesions were examined by the deparaffinized flow cytometric technique for DNA content. DNA-aneuploid tumors were considered to correlate if the DNA indices (ratio of aneuploid to diploid peak channels) were within 10%. Thirty-four tumors were DNA-aneuploid; eight tumors were DNA-diploid. We found agreement in 20 of 22 cases (agree-aneuploid: 16 cases; agree-diploid: four cases). In six of our cases the histograms of the primary and the metastatic lesions did not correlate when only one block was examined; however, when three blocks from each site were studied, we found concordance of DNA indices in four cases. There was disagreement in two of 22 cases (disagree-different DNA indices: two cases). In both of these cases, only one block of the primary tumor was available for examination, and the histograms were of marginal quality. This study demonstrates that the histogram pattern (aneuploid versus diploid) of DNA content is highly conserved between primary and metastatic tumors. There was 91% agreement between DNA indices of primary tumors and their metastases (20 of 22 cases) using a 10% correlation criterion. These data indicate that flow cytometric DNA analysis offers supportive information but not diagnostic confirmation of the origin of a metastatic lesion.