Gastrointestinal stromal tumor with dedifferentiation to undifferentiated pleomorphic sarcoma

De novo dedifferentiated SDH-deficient gastrointestinal stromal tumor with MDM2 amplification: case report and literature review

The dedifferentiation of the gastrointestinal stromal tumors (GISTs) has been reported in a small number of cases, usually under the pressure of the tyrosine kinase inhibitor (TKI) treatment. Herein, we described a de novo dedifferentiated GIST with the SDH deficiency in a 32-year-old Chinese woman. The tumor was located on the lesser curvature of the gastric antrum, measuring 4.1x9.1 cm2. Microscopically, the tumor was composed of 2 distinct morphological populations, mild epithelioid cells arranged in the multinodular growth pattern and hyperchromatic spindle cells arranged in the fascicular or sheet-like architecture. The two zones showed different immunophenotypes. The former proved to be an epithelioid GIST with the positive expression for C-KIT, DOG-1, and CD34, and the latter expressed the CKpan and P53, but negative for the C-KIT, DOG-1, and CD34. However, the SDHB staining was negative in both areas. Genetically, the next-generation sequencing (NGS) analysis showed the SDHC mutation (p.S48*) in both components and the MDM2 amplification was only in the spindle cell area. The lesion was diagnosed as the SDH-deficient GIST with the epithelial cell dedifferentiation. We proposed that the P53 associated gene alteration or other alternative escape mechanisms for the KIT-independent signaling pathways might play a role in the dedifferentiation.

Gastrointestinal Stromal Tumor With Chondrosarcomatous Dedifferentiation Following Imatinib Therapy

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the digestive tract, followed by schwannomas, lipomas, leiomyomas, and vascular tumors. They arise more often in the stomach, followed by the small bowel, esophagus, and rectum. Imatinib mesylate, a tyrosine kinase inhibitor with activity against ABL, BCR-ABL, platelet-derived growth factor receptor-alpha (PDGFRA), and c-KIT (CD117), constitutes the cornerstone of treatment for inoperable or metastatic GIST. Cases showing disease progression or resistance to imatinib mesylate may retain their morphology or present unusual morphologic and immunohistochemical characteristics.

We herein describe a case of a 67-year-old patient with a previous history of GIST of the stomach, with local recurrence, who was admitted with a workup of lung nodule on chest computed tomography as part of the routine follow-up. The nodule was resected which showed a malignant tumor composedof epithelioid cells, with an abrupt transition to chondrosarcoma. Epithelioid cells were immunostained for CD117, DOG1, and Vimentin, whereas chondrosarcomatous cells expressed only Vimentin. These findings were consistent with metachronous pulmonary metastasis of the previously diagnosed GIST with chondrosarcomatous dedifferentiation. No KIT or PDGFRA mutation was detected. A review of all accessible pertinent papers disclosed 26 similar cases with unusual morphological and immunohistochemical findings, either post-imatinib treatment or, less commonly, de novo, with heterogeneous differentiation.

Awareness of the histological and immunohistochemical changes in GISTs post imatinib therapy is essential to avoid a severe diagnostic pitfall.

Rare case of a duodenal de novo dedifferentiated gastrointestinal stromal tumour

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. Dedifferentiation in these tumours occurs rarely, and when it does occurs most commonly after prolonged treatment with imatinib. We report the case of a 64-year-old man who presented with a mass of 8×7×3 cm dimensions involving the duodenum and head of the pancreas. On histopathology, areas of anaplastic tumour cells were negative for DOG-1, c-kit, CD-34, desmin and panCK along with a molecular level study showing wild-type KIT and PDGFRA (platelet-derived growth factor receptor alpha) gene. Based on focal GIST-like areas and CD117 positivity and absence of prior therapy, the diagnosis of a de novo dedifferentiated GIST was made. These tumours need to be reported as they pose a diagnostic challenge and their predicted response rated to targeted molecular therapies are unclear as compared with their c-kit positive counterparts.

Coexistence of gastrointestinal stromal tumor and leiomyosarcoma of the stomach presenting as a collision tumor: A case report and review of literature

Collision tumor of the stomach is rare. We report a rare case of a gastric collision tumor consisting of gastrointestinal stromal tumors (GISTs) and leiomyosarcoma (LMS). Computed tomography scan revealed a 15 cm sized mass in the posterior wall of the body of the stomach. Gross examination of the wedge resection specimen showed the tumor located in the muscularis propria with extramural protrusion into the peritoneal cavity and the gastric cavity with geographic necrosis, hemorrhage, and mucosal ulceration. Histologically, the majority of the tumor consisted of the GIST component and the minor area in the submucosal region consisted of the LMS component. The tumor showed an abrupt transition between GIST and LMS by histologically and immunohistochemically, suggesting a collision tumor. Furthermore, the GIST components exhibited a c-kit exon 11 mutation. On the other hand, LMS component exhibited neither c-kit nor platelet-derived growth factor receptor-alpha (PDGFRA) mutation. Here we describe a case of the collision tumor consisting of GIST and LMS and its literature review.