A 52-year old woman presented with signs and symptoms of thoracic spinal cord compression caused by a spinal canal mass extending from the seventh to the ninth thoracic vertebra. Initial treatment consisted of high dose steroids and decompression laminectomy with subtotal resection of the abnormal mass. Sheets of immature myeloid cells which expressed the t(15;17)(q22;q21) of acute promyelocytic leukemia (APL) by fluorescence in situ hybridization (FISH) were present, consistent with promyelocytic sarcoma. Bone marrow examination showed no evidence of acute leukemia. She was then placed on the PETHEMA (Programa para el Tratamiento de Hematopatias Malignas, a Spanish cooperative chemotherapy group) regimen for APL for 15 months. There has been no evidence of local recurrence or of systemic APL at the 4.5-year mark, the longest follow-up of isolated promyelocytic sarcoma in the medical literature.