A Retroperitoneal Dedifferentiated Liposarcoma Producing Granulocyte Colony-Stimulating Factor Accompanied by Spontaneous Rupture: PET/CT Imaging of a G-CSF-Producing Tumor

The patient was a 63-year-old man who was referred to our hospital as an emergency case with the chief complaint of abdominal pain. An abdominal CT revealed a right retroperitoneal tumor of 15 cm and retroperitoneal bleeding. After a transcatheter arterial embolization was performed, the patient was transferred to our department. There was no infective focus. The white blood cell (WBC) count (37,820/μl, normal range <8 pg/ml) and the serum granulocyte colony-stimulating factor (G-CSF) level (2,670 pg/ml, normal range <8 pg/ml) were high. Bone marrow biopsy revealed little fat, significant hyperplasia, and predominantly increased neutrophils, but no findings of bone metastasis or bone marrow involvement. A G-CSF-producing tumor was diagnosed and right nephrectomy and retroperitoneal tumorectomy were performed. However, the tumor had infiltrated into the inferior vena cava, diaphragm and abdominal wall, and only part of the tumor could be removed. In histopathological tests, hematoxylin-eosin staining showed malignant fibrous histiocytoma-like findings mixed with those for well-differentiated liposarcoma, and the case was diagnosed as dedifferentiated liposarcoma. Preoperative (18)F-FDG-PET computed tomography showed diffuse (18)F-FDG uptake throughout the bone marrow and elevated uptake at the tumor site. However, since bone biopsy and bone scintigraphy indicated no bone metastasis or bone marrow involvement, we concluded that PET/CT imaging gave false-positive results in the bone marrow. This is the first report of PET/CT imaging of a G-CSF-producing tumor in a urological disease. The imaging results may be useful for differential diagnosis for this tumor in patients with high WBC counts without infection.