Biphasic GISTs reveal the early mechanisms in GIST high-grade transformation. Homo sapiens

To study the very early changes in high-grade transformation of gastrointestinal stromal tumors (GISTs), 17 biphasic GISTs, with a transitional status in which low-grade and high-grade parts coexist, were collected from 263 continuous cases (6.5%). Nucleic acids of each part were retrieved for gene expression profiling. Overall design: By definition, biphasic GISTs contained two populations of neoplastic cells that were (1) morphologically different, either in abrupt or gradual transition to the other, and (2) showed a dramatic change in mitotic activity, which was defined as either (a) one population had ≤ 5 mitoses per 5 mm2 (AJCC G1) and the other had > 5 mitoses per 5 mm2 (AJCC G2), or (b) both populations were AJCC G1, but the difference in mitotic activity was equal to or more than 3 per 5 mm2, or (c) both populations were AJCC G2, but the low-grade part was in the range of > 5 and ≤ 10 mitoses per 5 mm2 and the high-grade part exceeded it by equal to or more than 5 mitoses per 5 mm2. In each case, selected low-grade area, high-grade area and normal smooth muscle area (as control) were manually microdissected. RNA was extracted with the RecoverAll™ Total Nucleic Acid Isolation Kit FFPE (Life Technologies, Taipei, Taiwan).