Nuclear DNA content and distribution of Ki-67 positive cells in nodular fasciitis

Nodular fasciitis (NF) is regarded as a disease of reactive growth of fibroblasts, although it frequently shows clinically rapid growth and sometimes has to be histologically discriminated from fibrosarcoma. In order to confirm the position of NF as a benign tumor, we studied 5 cases of NF by a quantitative analysis of the nuclear DNA content using flow cytometry in paraffin-embedded specimens. In 3 of the 5 cases, an immunohistochemical study using Ki-67 monoclonal antibody was also conducted in frozen sections. In the analysis of nuclear DNA content, DNA histograms showed a diploid pattern in all cases, and G1, S and G2 + M periods were calculated as 96.7%, 2.5% and 0.8% (on the average), respectively. Although the labeling index of Ki-67 antibody (positive cells/tumor cells; %) was as scattered as 1.3-7.8 (5.6 on the average), the mean value was higher than that in already reported dermatofibroma and dermatofibrosarcoma protuberans and lower than that in malignant fibrous histiocytoma. These results endorse the hypothesis that NF is a reactive benign disease and reflect the biological behavior of this disease, which may frequently show rapid growth.