Extra-gastrointestinal stromal tumor arising in the lesser omentum with a platelet-derived growth factor receptor alpha (PDGFRA) mutation: a case report and literature review

Molecular Profiling of KIT/PDGFRA-Mutant and Wild-Type Gastrointestinal Stromal Tumors (GISTs) with Clinicopathological Correlation: An 18-Year Experience at a Tertiary Center in Kuwait

In gastrointestinal stromal tumors (GISTs), identifying prototypical mutations in the KIT/PDGFRA oncogenes, or in rare alternate genes, is essential for prognostication and predicting response to tyrosine kinase inhibitors. Conversely, wild-type GISTs (WT-GIST), which lack known mutations, have limited treatment options. Data on the mutational landscape of GISTs and their impact on disease progression are very limited in Kuwait. Using a targeted next-generation sequencing panel, we investigated the spectrum and frequency of KIT, PDGFRA, and RAS-pathway-related mutations in 95 out of 200 GISTs diagnosed at Kuwait Cancer Center from 2005 to 2023 and assessed their correlation with clinicopathological parameters. Among the 200 tumors (median age 55 years; 15-91), 54% originated in the stomach, 33% in the small bowel, 7% in the colorectum, 1.5% in the peritoneum, and 4.5% had an unknown primary site. Of the 95 molecularly profiled cases, 88% had a mutation: KIT (61%), PDGFRA (25%), NF1 (2%), and one NTRK1 rearrangement. Ten WT-GISTs were identified (stomach = 6, small bowel = 2, and colorectum = 2). WT-GISTs tended to be smaller (median 4.0 cm; 0.5-8.0) (p = 0.018), with mitosis ≤5/5 mm2, and were of lower risk (p = 0.019). KIT mutations were an adverse indicator of disease progression (p = 0.049), while wild-type status did not significantly impact progression (p = 0.934). The genetic landscape in this cohort mirrors that of global studies, but regional collaborations are needed to correlate outcomes with genetic variants.

Clinicopathological and therapeutic analysis of PDGFRA mutated gastrointestinal stromal tumor

BACKGROUND

Platelet-Derived Growth Factor Receptor Alpha (PDGFRA) mutation has causes a rare subgroup of gastrointestinal stromal tumor (GIST) and not too much attention has been paid on it until the appearance of Avapritinib. This study aims to explore the clinicopathological features, therapy and prognosis of PDGFRA-mutant GIST for better understanding and clinical practice.

METHOD

119 PDGFRA-mutant GIST patients were retrospectively collected from 2038 patients who underwent genetic testing. Kaplan-Meier method was used.

RESULTS

The incidence rate of PDGFRA-mutant GIST in our center was 5.8 %, with 79 males, 40 females, and a median age of 57 (25⁃80) years old. All the tumors were in the stomach, among which 60 were epithelioid type, 25 were spindle type and 34 were mixed type. There were 13 cases of exon 12 mutation and 106 cases of exon 18 mutation including 83 cases of D842V mutation (69.7 %). During a median follow⁃up of 49.6 (range, 1⁃154) months, progression could be observed in 12 patients with gene mutation at the codon 842 of exon 18, another case was V561D mutation in exon 12. The 5-year diseases⁃free survival (DFS) was 90.1 %, which was associated with the loss of CD34 expression (P＜0.001). Patients in D842V group showed a marginal worse prognosis than those in non-D842V group (P = 0.163). According to the NIH criteria, high risk group showed a poorer prognosis than non-high risk group (P = 0.003), however, there were no significant differences among the three non-high risk groups (P = 0.495, P = 0.652). Among 13 advanced patients, 5 cases (treated with Avapritinib) achieved partial remission.

CONCLUSION

PDGFRA-mutant GIST mostly derived from stomach, with a relative indolent behavior. D842V mutation and lose of CD34 expression were adverse prognostic factors. Avapritinib can effectively control advanced patients in a certain period of time.

Current knowledge of primary prostatic extra-gastrointestinal stromal tumor: a case report and review of the literature

The patient was a 62-year-old man diagnosed as having prostatic extra-gastrointestinal stromal tumor (EGIST) who was treated with imatinib. No recurrence or metastasis was found after a 6-month follow-up. We identified 14 cases of prostatic primary EGIST in PubMed and summarized these cases with our case. The patients' ages ranged from 31 to 78 years (average: 53.6 years), and most patients' prostate-specific antigen (PSA) concentrations were within normal limits (92.9%, 13/14). All patients underwent imaging examinations; prostatic masses measured 6 to 14.2 cm (mean: 9.43 cm), and imaging excluded secondary prostatic masses from the intestinal tract. By immunohistochemical staining, the tumors were positive for cluster of differentiation (CD)117 (71.4%, 10/14), DOG1 (100%, 7/7), and CD34 (100%, 14/14), and negative for smooth muscle actin (SMA) (71.4%, 10/14), desmin (100%, 11/11), and S100 (100%, 12/12). Treatment depended on the results of the gene mutation detection as well as the risk estimation according to tumor size and microscopic mitotic rates (>5 per 50 high-power fields: 60%, 6/10). Among the 12 patients with reported outcomes, nine achieved good results (no recurrence or metastasis), one achieved reduced mass volume, one experienced recurrence, and one died.