Abstract
Eosinophilia is a common systemic reaction to allergy, parasitic infection, or drug hypersensitivity. Rarely, it manifests as a paraneoplastic phenomenon, most commonly secondary to hematologic malignancies or extensive metastatic disease in solid tumors. There is scarce literature attributing peripheral eosinophilia to solid organ malignancies, especially gynecologic malignancies. We present the first reported case of peripheral eosinophilia secondary to high-grade endometrial stromal sarcoma (HGESS). A postmenopausal woman presented with weakness, urinary incontinence, and marked peripheral eosinophilia. An unremarkable infectious workup prompted further imaging, which revealed a uterine mass. She underwent total hysterectomy with bilateral salpingo-oophorectomy, after which her eosinophilia resolved. Histopathology confirmed HGESS. One month later, the patient re-presented with recurrent eosinophilia and was found to have new metastatic lesions on CT abdomen/pelvis. She elected to pursue hospice care. This case highlights a rare and atypical presentation of an aggressive uterine malignancy underscoring peripheral eosinophilia as a potential marker of underlying malignancy.