A Case Report of Chronic Expanding Hematoma of the Left Erector Spinae Muscle After Stereotactic Body Radiotherapy for Renal Cell Carcinoma

Background: Hematomas that slowly increase in size for over a period of more than one month after the initial hemorrhage are referred to as chronic expanding hematoma (CEH). We report a case of CEH of left erector spinae muscle after stereotactic body radiotherapy (SBRT) for renal cell carcinoma (RCC). Case presentation: A 74-year-old Japanese male complained of back pain. There was no history of surgery or trauma of his back. He received SBRT for RCC of left kidney of seven years ago. Computed tomography (CT) revealed the left erector spinae muscle was swollen compared to the contralateral side at the third lumbar level. Ultrasonography showed a tumor of 30 mm in size without blood flow in left paraspinal muscle. Positron emission tomography-CT revealed uptake in the left paraspinal muscle. Pathological examination showed radiation-induced CEH. We performed conservative therapy with medication alone because the tumor had been gradually growing. One year after starting observation, the patient died due to subdural hemorrhage after a fall and progression of renal failure. Discussion and conclusions: Because this study was a case study, it is difficult to definite the CEH after SBRT. Since SBRT has recently been increasing, SBRT-induced CEH is considered to be an important complication.