Contributed by Abdul-Haseeb Naeem1, Matthew Kubica2, Amirpouyan Namavarian3, Sachin Pandey4, Qi Zhang2
1Department of Clinical Neurological Sciences, 2Department of Pathology and Lab Medicine, 3Department of Medical Science, 4Department of Medical Imaging, Western University, Ontario, Canada
CLINICAL HISTORY AND IMAGING
A 63-year-old male immigrant from Hong Kong presented with a 2-day history of urinary retention. On examination, he had a cauda equina syndrome. Imaging by CT and MRI revealed a large L2- L3 disc herniation and spinal stenosis. An emergency bilateral L2 laminectomy and L2-L3 discectomy resolved his pre-operative symptoms. However, the MRI scan had also identified a sclerotic lesion at the left T12 pedicle, characterised by abnormal bone marrow T1 hypointensity (Figure 1a) and T2 hyperintensity (Figure 1b), suggesting a metastasis. However, a primary site was not identified in CT scans of the chest, abdomen and pelvis, and a skeletal survey and an isotope bone scan did not reveal any other bone lesions. A fluoroscopic guided biopsy of the left T12 pediclular lesion was carried out.
The biopsy specimen consisted of multiple fragments of hemorrhagic tan tissue measuring 5.0 x 0.4 x 0.3 cm in aggregate. Microscopic examination of the sections showed fragments of lamellar bone and blood clot. There were also abundant multi-vacuolated foamy cells in the bone marrow (Figure 1c). These cells were immunopositive for S100 (strong, cytoplasmic) and immunonegative for CD68 and cytokeratin (AE1/AE3, CAM 5.2). The residual bone marrow was unremarkable and exhibited trilineage differentiation and a full spectrum of maturation. There was no hemosiderin or evidence for a healing fracture. Special stains (PAS+/-D, Congo red, GMS) were noncontributory (Figure 1d). What is your diagnosis?