PDGFRA mutant gastrointestinal stromal tumor with composite sclerosing and inflammatory myofibroblastic tumor-like morphology, a case report

Background

Gastrointestinal stromal tumors are the most common mesenchymal tumors of the stomach and small bowel. Their myriad morphology sometimes renders the diagnosis very challenging.

Case presentation

The 57 years old man was admitted to hospital for a gastric mass found in a routine physical examination. Gastroscopy examination showed scattered mucosa congestion and edema, there were no ulcer or mass. Computed tomography scan uncovered a round shadow in the right upper abdominal cavity, closely related to the gastric antrum. The patient underwent tumor resection and partial gastrectomy. On gross examination of the specimen the tumor was 7 cm × 5 cm × 5 cm and the cut surface was greyish white with multifocal small cysts. Microscopically, there are two sharply separated morphologic pattern. One side was hypocellular with short spindle cell randomly distributed in sclerosing stroma in which are some branched staghorn-like vessels, mimicking solitary fibrous tumor. The other side was cellular with loose bundle-like growth of spindle cells in fibromyxoid stroma with lymphocytes infiltration, mimicking inflammatory myofibroblastic tumor. The number of mitosis was less than 5 per 5 mm² field. There was no necrosis. Immunophenotypically, the spindle cells were focally CD117 weakly positive and Dog1 positive. They were negative for S100, MDM2, ALK, CK-pan, CD34, CDK4, STAT6, SMA, desmin. SDHB expression was intact. Gene sequencing revealed PDGFRA exon 18 mutation (D842V). The final diagnosis was gastrointestinal stromal tumor, low risk. The patient was followed up with 10 months after operation, no recurrence or metastasis was found.

Conclusion

We present an unusual case of gastrointestinal stromal tumor harboring PDGFRA p.D842 mutation with unusual morphology. Our case expanded the morphological spectrum of those tumors, recognizing this rare morphological variation of the tumor would avoid misdiagnosis and inappropriate treatment.