Clinical importance of tumor rupture in gastrointestinal stromal tumor.

Risk factors of gastrointestinal stromal tumors (GISTs) include tumor size, location, mitosis, and tumor rupture. Although the first three are commonly recognized as independent prognostic factors, tumor rupture is not a consistent finding. Indeed, tumor rupture may be subjectively diagnosed and is rarely observed. Moreover, the criteria used for diagnosis differ among oncologists, which may result in inconsistent outcomes. Based on these conditions, a universal definition of tumor rupture was proposed in 2019 and consists of six scenarios: tumor fracture, blood-stained ascites, gastrointestinal perforation at the tumor site, histologically proven invasion, piecemeal resection, and open incisional biopsy. Although the definition is considered appropriate for selection of GISTs with worse prognostic outcomes, each scenario lacks a high level of evidence and there is yet no consensus for some, including histological invasion and incisional biopsy. It may be, however, important to have common criteria for clinical decision-making, which may facilitate reliability, external validity, and comparability of clinical studies in rare GISTs. After the definition, several retrospective reports indicated that even with adjuvant therapy, tumor rupture was associated with high recurrence rates and poor prognostic outcomes. The prognosis of patients with ruptured GISTs is improved by 5-year adjuvant therapy compared with 3-year therapy. Nevertheless, the universal definition requires further evidence, and prospective clinical studies based on the definition are warranted.