Objective:

To present a case of primary gastric undifferentiated pleomorphic sarcoma (UPS) misdiagnosed as gastrointestinal stromal tumor (GIST), highlighting the clinical implications of such misdiagnosis and reviewing existing literature on this rare condition.

Key Findings:

• Primary gastric UPS is exceedingly rare and often misdiagnosed due to nonspecific clinical presentation.
• Histopathological and molecular analyses are crucial for accurate diagnosis and can guide treatment decisions.
• The patient experienced rapid tumor recurrence despite adjuvant chemotherapy, underscoring the aggressive nature of UPS.

Interpretation:

The case highlights the aggressive nature of primary gastric UPS and emphasizes the need for increased awareness and consideration of UPS in the differential diagnosis of gastric soft tissue masses.

Limitations:

• Limited epidemiological data on UPS.
• Challenges in preoperative diagnosis due to similarities with GIST, suggesting a need for improved diagnostic protocols.

Conclusion:

This case emphasizes the urgent need for improved diagnostic and therapeutic strategies for primary gastric UPS, given its aggressive behavior and poor prognosis, and highlights the importance of awareness among clinicians.