Paraffin-embedded archival tissue samples were used for determination of
DNA ploidy by flow cytometry on 117 surgically resected gastric
smooth muscle tumors (44
leiomyosarcomas, 53
leiomyomas, and 20 benign
leiomyoblastomas). 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 53
leiomyomas, the
DNA ploidy pattern was diploid in most
tumors (87%), except for 2
DNA tetraploid/
polyploid and 5
DNA aneuploid samples. In comparison, the 20 benign
leiomyoblastomas had more frequent abnormal
DNA histograms:
DNA tetraploidy/
polyploidy in 5 (25%) and
DNA aneuploidy in 2 (10%). The
DNA histograms of the 44
leiomyosarcomas (including 4
epithelioid leiomyosarcomas) were classified as follows: 20 cases (45%) exhibited
a DNA diploid pattern, 14 cases (32%) had
a DNA tetraploid/
polyploid pattern, and 10 cases (23%) had
DNA aneuploid peaks. For the patients with
leiomyosarcomas, the
DNA ploidy pattern was significantly correlated with survival (P less than 0.001), as were
tumor grade (P less than 0.001) and
tumor size (P less than 0.05). Furthermore, both benign and malignant gastric
smooth muscle tumors with
DNA tetraploid/
polyploid patterns were significantly larger than those with
a DNA diploid histogram (P less than 0.05).
DNA ploidy pattern cannot be used for diagnosis--that is, to distinguish malignant from benign gastric
smooth muscle tumors. For gastric
leiomyosarcomas, however, nuclear
DNA ploidy pattern is an easily measured objective determination with important prognostic significance.