Hypereosinophilic syndrome mimicking gastric malignancy: considerations on the challenging diagnosis—a case report and review of the literature

Hypereosinophilic syndromes (HES) are rare disorders characterized by the abnormal accumulation of eosinophils, which can lead to organ damage. The clinical manifestations are highly variable and can sometimes mimic tumors, presenting significant diagnostic challenges. This case report emphasizes the difficulty of diagnosing HES, particularly when it presents as a gastric pseudotumor, and the essential role of pathological examination in guiding diagnosis and treatment. A 51-year-old Chinese Han female with a history of elevated eosinophils presented with epigastric pain, weight loss, and fatigue. Imaging suggested a gastric malignancy with possible metastasis. Despite these findings, biopsies revealed eosinophilic infiltration without malignancy. Based on persistent eosinophilia and multi-organ involvement, HES was diagnosed. The patient was treated with corticosteroids, resulting in significant clinical improvement, confirmed by follow-up imaging and endoscopic examination. This case highlights the importance of distinguishing HES from malignancies to avoid unnecessary surgical interventions. Early recognition and appropriate corticosteroid treatment can lead to significant improvement, underscoring the importance of careful diagnostic evaluation in cases with ambiguous clinical presentations.