816 A Benign Diagnosis for Suspected Malignant Differential of a Sacral Lytic Lesion.

Abstract

Abstract 49-year-old relatively healthy man presented to the ER with abdominal and associated low back pain. Past history was significant for excision of spinal benign tumor excision and 30-year pack history of smoking. Review of systems was significant for recurrent leg swelling and muscle aches. Neurological exam was non focal. CT scan of the abdomen and pelvis revealed a lytic sacral lesion with soft tissue component. The rest of the skeletal survey and system evaluation was unremarkable. Patient was referred to Oncology, suspecting the localized plasmacytoma variant of multiple myeloma with an inconclusive sacral mass biopsy report. Full blood count, comprehensive metabolic panel, Beta-2 microglobulin serum protein electrophoresis (SPEP), and free light chains assays undertaken were all within normal ranges. Further second opinion was sought for the biopsy results to undertake special stains which concluded the biopsy as schwannoma. In view of the persisting recurring pain and swelling, further MRI imaging and IR guided biopsy was suggested. However, the patient was with limited insurance coverage. He opted to defer further evaluation and adopted a “wait and see” approach and has since remained stable. Sacral schwannomas are rare. It is possible that his previous extradural lesion could have been a schwannoma. Schwannomas are slow growing and relatively asymptomatic. As they are typically lytic lesions can easily be mistaken for malignant lesions and have to be considered in the differential of osteolytic lesions as they can grow in close proximity to bony structures.