Contributed by Gerald F. Reis MD, PhD, Arie Perry MD
Department of Pathology, Division of Neuropathology, University of California San Francisco, San Francisco, California
The patient is a 67-year-old man with a history of hypertension and coronary artery disease who presented with progressively worsening low back pain for 1 year. He underwent a laminectomy for lumbar spinal stenosis 17 years prior and had done very well after the procedure. Review of systems was negative for weakness as well as bowel or bladder dysfunction. Physical exam revealed normal strength in the upper and lower extremities. Spine films showed lumbar levoscoliosis, multilevel degenerative lumbar disease, and lumbar lordosis with normal pelvic tilt. MRI of the spine showed multilevel degenerative disc disease and an incidental intradural, intramedullary mass at L1-L2 (Figures 1 and 2). The radiologic diagnosis was schwannoma, and the differential included ependymoma and neurofibroma. The patient presented to this institution for a second opinion. He chose to undergo surgery for tumor resection.
Intraoperative evaluation demonstrated a benign spindle cell lesion with multiple foci of mineralization. Review of permanent H&E sections showed soft tissue with numerous needle-shaped crystals arranged radially as a fan and surrounded by a bland population of spindle cells, granulation tissue, mild chronic inflammation, and hemosiderin-laden macrophages (Figures 3, 4, 5). Mitotic figures were inconspicuous. No necrosis was seen. The crystals demonstrated positive birefringence on polarizable light (Figure 6). What is the diagnosis?