A Case of G-CSF-Producing Histiocytic Sarcoma of the Stomach.

No reports have been published to date regarding primary gastric granulocyte colony-stimulating factor (G-CSF)-producing histiocytic sarcoma. We encountered a case of primary gastric histiocytic sarcoma that also fulfilled the criteria for a G-CSF-producing tumor. A 75-year-old man was diagnosed with gastric cancer with poorly differentiated adenocarcinoma. The patient's white blood cell count was elevated to 20,700/μL, and the G-CSF level was elevated to 380 pg/mL. A computed tomography scan showed hepatic infiltration; therefore, a preoperative diagnosis of T4 (liver) N2H0M0 cStage IV gastric cancer was made, and surgery was performed. No. 11d lymphatic metastasis was noted, resulting in invasion of the pancreatic tail, and combined resection of the liver, pancreas, and spleen was conducted with complete gastrectomy. The results of hematoxylin-eosin and immunohistochemical staining were subsequently assessed. On discharge, the G-CSF level had fallen to 22.7 pg/mL. Currently, the patient is still alive and has experienced no recurrence approximately 4 years after the operation.