Tumor Lysis Syndrome due to Eribulin Administration for Metastatic Undifferentiated Pleomorphic Sarcoma of the Buttock

Tumor lysis syndrome (TLS) is a complication of cancer treatment that requires urgent intervention. It is extremely rare in the treatment of soft tissue sarcoma (STS) of the limbs or trunk, and there are currently no reports of TLS occurrence from eribulin therapy. We report the case of a 78-year-old woman with an undiffer-entiated pleomorphic sarcoma on the right buttock. We initiated chemotherapy with intravenous eribulin mesylate. Deterioration of renal function, mild hyperkalemia, hyperuricemia, hypocalcemia, and hyperphos-phatemia were confirmed on examination, suggesting the presence of TLS. We present an extremely rare case of TLS from eribulin for STS.