Uterine leiomyosarcomas and benign smooth muscle tumors: usefulness of nuclear DNA patterns studied by flow cytometry

Flow cytometry was used to determine the DNA ploidy pattern of paraffin-embedded archival tissue specimens from 90 surgically resected uterine smooth muscle tumors (49 leiomyosarcomas and 41 leiomyomas). The technique of Hedley was used for preparation of paraffin-embedded tissue into single dissociated nuclei, and the method of Vindeløv was used for staining with propidium iodide. Among the 41 leiomyomas, most tumors (88%) had a DNA diploid pattern; the exceptions were two DNA tetraploid/polyploid and three DNA aneuploid samples. The DNA histograms of the 49 leiomyosarcomas (including 6 epithelioid leiomyosarcomas) were classified as follows: 9 cases (18%) exhibited a DNA diploid pattern, 29 cases (59%) had a DNA tetraploid/polyploid pattern, and 11 cases (23%) had DNA aneuploid peaks. Although DNA ploidy pattern cannot be used diagnostically to distinguish malignant from benign uterine smooth muscle tumors, the nuclear DNA ploidy pattern is an easily measured, objective determination that may have important prognostic significance for patients with uterine leiomyosarcomas.