Granulocyte colony‐stimulating factor producing retroperitoneal leiomyosarcoma

INTRODUCTION: Granulocyte colony‐stimulating factor‐producing nonhematopoietic malignancies have poor clinical outcomes. CASE PRESENTATION: A 62‐year‐old woman complaining of fever and left lower quadrant pain was referred to our hospital. A left retroperitoneal tumor was suspected on computed tomography, and laboratory data showed leukocytosis and markedly elevated granulocyte colony‐stimulating factor. She underwent left nephroureterectomy, partial colectomy, and psoas muscle resection. The histological examination showed a granulocyte colony‐stimulating factor‐producing retroperitoneal leiomyosarcoma. Three months after the operation, she developed lung and liver metastases and received the chemotherapy, including doxorubicin and ifosfamide. Eight months after the operation, these lesions had progressed, and a new bone metastasis appeared. Twelve months after the operation, she received pazopanib and radiation for bone metastases. However, the metastases progressed, and she died 17 months after the operation. CONCLUSION: Since granulocyte colony‐stimulating factor‐producing retroperitoneal leiomyosarcoma had a very poor prognosis irrespective of intensive treatment including wide resection, effective systemic therapy should be required.