Distinct biphasic histomorphological pattern in gastrointestinal stromal tumours (GISTs) with common primary mutations but divergent molecular cytogenetic progression

Prognostic value of metabolic tumor volume and total lesion glycolysis on preoperative 18F-FDG PET/CT in patients with localized primary gastrointestinal stromal tumors

Background

This study aimed to evaluate the prognostic value of pretreatment ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) in patients with localized primary gastrointestinal stromal tumors (GISTs) and to compare the predictive values of ¹⁸F-FDG PET/CT parameters with those of clinicopathological prognostic factors.

Methods

Sixty-two localized GIST patients who underwent staging with ¹⁸F-FDG PET/CT from January 2007 to December 2013 before surgery were retrospectively enrolled. A volume of interest with a standardized uptake value (SUV) threshold of 2.5 was used to determine the metabolic tumor volume (MTV) and total lesion glycolysis (TLG). These metabolic indices, along with the maximum SUV (SUVmax), were analyzed to evaluate recurrence-free survival (RFS). Other significant clinical and pathologic indices were also retrospectively reviewed for RFS analysis.

Results

Patients were followed up for a median of 42.0 months (range, 5.6–111.5). During the follow-up period, 13 patients (21.0%) experienced disease recurrence. In univariate analysis, tumor size (> 5 cm), mitotic count (> 5/high-power field), modified National Institutes of Health (NIH) consensus criteria, adjuvant imatinib treatment, SUVmax (≥ 7.04), MTV (≥ 50.76 cm³), and TLG (≥ 228.79 g) were significant prognostic factors affecting RFS (p < 0.05). In multivariate analysis, only MTV (hazard ratio, 17.69; 95% confidence interval [CI], 2.03–154.17, p = 0.009) and TLG (hazard ratio, 20.48; 95% CI, 2.19–191.16, p = 0.008) were independent prognostic factors for RFS. The 5-year RFS rates were 96.4% and 96.6% in patients with a low MTV and TLG and 27.3% and 23.6% in patients with a high MTV and TLG, respectively (p < 0.001).

Conclusion

MTV and TLG are independent prognostic factors for predicting recurrence in patients with localized primary GIST. Patients with a high MTV or TLG are at risk for poor prognosis and should be closely observed for disease recurrence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40170-021-00244-x.

Loss of SFRP1 expression is a key progression event in gastrointestinal stromal tumor pathogenesis

The mechanism of high-grade transformation in gastrointestinal stromal tumors (GISTs) remains to be clarified. We aim to discover the key progression events by studying biphasic GISTs. The study group included 101 GISTs. Nineteen of these had been screened from 263 GISTs to represent the early stage of GIST high-grade transformation, characterized by juxtaposed low-grade and high-grade regions in the same tumor (so-called biphasic GISTs). Mutational analyses, fluorescence in situ hybridization (FISH), NanoString analyses, telomere analysis, and gene expression profiling were carried out, followed by in silico analyses, cell line study, and immunohistochemical validation. Using gene expression analysis, downregulation of SFRP1 was revealed to be the main event in GIST high-grade transformation (p = 0.013), accompanied by upregulation of EZH2. In silico analyses revealed that downregulation of SFRP1 was a common feature in GIST progression across several different series. Immunohistochemically, the expression of SFRP1 was validated to be significantly lower in high-grade GISTs (WHO risk group 3a or higher) than in low-grade GISTs (p < 0.001), and attenuation/loss of SFRP1 was associated with GIST tumor progression (p < 0.001). By NanoString and FISH analyses, chromosomal 9/9p loss was the only recurrent large-scale chromosome aberration in biphasic GISTs, with a correlation with SFRP1 downregulation. Subclones containing chromosome 9/9p loss could be appreciated in the low-grade parts of biphasic GISTs. TP53 mutation, RB1 loss, KIT/PDGFRA mutation, and alternative lengthening of telomeres did not play a significant role in GIST high-grade transformation. In conclusion, high-grade transformation of GISTs features SFRP1 downregulation and chromosome 9/9p loss.

[Clinical and morphological characteristics of gastrointestinal stromal tumors]

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Despite this, GISTS comprise about 2% in the structure of digestive tract cancers. They are usually localized in the stomach; however, they can be found in the small intestine and more rarely in the colon and esophagus. Although approximately 70% of the GISTs consist predominantly of spindle cells; the epithelioid cell tumors represent 20% of cases; there are also mixed variants. This variability in the morphological structure of GISTs complicates their diagnosis.

Gastrointestinal stromal tumor: recent advances in pathology and genetics

The discovery of KIT gene mutation in gastrointestinal stromal tumor (GIST) has provided a paradigm shift in the classification, diagnosis and molecular-targeted therapy of gastrointestinal mesenchymal tumors. There is growing evidence of phenotype-genotype (KIT, platelet-derived growth factor receptor-alpha, succinate dehydrogenase or other driver gene mutation) and genotype-therapeutic (sensitivity to imatinib) correlations in GIST. Risk stratification based on mitotic counts, tumor size and rupture is useful for the prognostication and management of patients with GIST. Blood vessel invasion is a strong indicator of liver metastasis in GIST. In addition, novel biomarkers such as cell-cycle regulators, microRNAs and their targets have been discovered by using high throughput molecular analyses. In contrast, leiomyosarcoma of the gastrointestinal tract has become a very rare entity in the 'KIT' era, and its molecular pathogenetic mechanism is unclear. Recent studies have revealed a wide spectrum of cytological atypia, mitotic counts and biological behavior of gastrointestinal smooth muscle tumors, suggesting the necessity of establishing the criteria for malignancy. Collectively, both classical histopathological procedures and modern molecular investigations are indispensable for the evolution of diagnosis and treatment of GIST and mimics.

Gastrointestinal stromal tumor and mitosis, pay attention

The difference between stages I and III of gastric gastrointestinal stromal tumor depends principally on the number of mitosis. According with TNM classification, the presence in the tumor of high mitotic rate determines the upgrading. Many studies exposed different count techniques in evaluating the number of mitosis. An international standardized method to assess mitotic rate is needed.

Advances in clinicopathological classification and genotyping of gastrointestinal stromal tumors

In recent years, the discovery of new markers and advances in mutation detection technologies have made it easy to diagnose gastrointestinal stromal tumor (GIST). However, it is still difficult to predict the biological behavior of GIST. Currently, the most prevalent GIST classification systems, including the National Institutes of Health (NIH) consensus criteria for assigning risk to gastrointestinal stromal tumors (2008 Revision) and the International Union Against Cancer TNM classification of malignant tumors (2010 version), are based on tumor size, mitotic rate, tumor location, and presence of a tumor rupture or not. Molecular genetic studies have shown that genotype of GIST is closely related to tumor prognosis and response to imatinib mesylate.

Epithelioid/mixed phenotype in gastrointestinal stromal tumors with KIT mutation from the stomach is associated with accelerated passage of late phases of the cell cycle and shorter disease-free survival

In gastrointestinal stromal tumors (GISTs), the occurrence of an epithelioid/mixed phenotype has been correlated to PDGFRA mutations, gastric localization and favorable outcome. On the other hand, the prognostic significance of an epithelioid/mixed growth pattern occasionally observed in GISTs with KIT mutation is unclear. The aim of this study was to evaluate the prognostic significance of an epithelioid/mixed phenotype in correlation to anatomical localization, genotype, and expression of cell-cycle markers in a series of 116 primary GISTs with KIT mutation on a tissue microarray. Independent of their anatomical localization, the majority of KIT-mutated GISTs displayed a pure spindled phenotype (72%), with the remaining tumors showing an epithelioid/mixed growth pattern. In KIT-mutated GISTs from the stomach, the occurrence of an epithelioid/mixed growth pattern was significantly correlated with larger tumor diameters (P=0.005), higher mitotic counts (P=0.0001), high-risk category (P=0.001), higher expression of the G2-phase cell-cycle marker cyclin B1 (P=0.04), higher expression of the G1 to M-phase proliferation marker Ki67 (P=0.02) and a significantly shorter disease-free survival (P=0.003) compared with tumors with pure spindled morphology. In contrast, there were no significant differences between pure spindled and epithelioid/mixed GISTs from the small/large bowel. Our findings indicate that the epithelioid/mixed phenotype in KIT-mutant gastric GISTs represents a secondary tumor growth pattern associated with tumor progression and adverse outcome, probably through accelerated G1/S-phase restriction point passage.

Cyclin H expression is increased in GIST with very-high risk of malignancy

BACKGROUND

Risk estimation of gastrointestinal stromal tumours (GIST) is based on tumour size and mitotic rate according to the National Institutes of Health consensus classification. The indication for adjuvant treatment of patients with high risk GIST after R0 resection with small molecule inhibitors is still a controversial issue, since these patients represent a highly heterogeneous population. Therefore, additional prognostic indicators are needed. Here, we evaluated the prognostic value of cyclin H expression in GIST.

METHODS

In order to identify prognostic factors of GIST we evaluated a single centre cohort of ninety-five GIST patients. First, GISTs were classified with regard to tumour size, mitotic rate and localisation according to the NIH consensus and to three additional suggested risk classifications. Second, Cyclin H expression was analysed.

RESULTS

Of ninety-five patients with GIST (53 female/42 male; median age: 66.78a; range 17-94a) risk classification revealed: 42% high risk, 20% intermediate risk, 23% low risk and 15% very low risk GIST. In patients with high risk GIST, the expression of cyclin H was highly predictive for reduced disease-specific survival (p = 0.038). A combination of cyclin H expression level and high risk classification yielded the strongest prognostic indicator for disease-specific and disease-free survival (p < or = 0.001). Moreover, in patients with tumour recurrence and/or metastases, cyclin H positivity was significantly associated with reduced disease-specific survival (p = 0.016) regardless of risk-classification.

CONCLUSION

Our data suggest that, in addition to high risk classification, cyclin H expression might be an indicator for "very-high risk" GIST.