Contributed by Ann E. Marshall1, Sarah E. Martin1, Narasimhan P. Agaram1, Jey-Hsin Chen1, Eric M. Horn2, Annette C. Douglas-Akinwande3, Eyas M. Hattab1
1Department of Pathology and Laboratory Medicine, 2Department of Neurological Surgery, and 3Department of Radiology, Indiana University School of Medicine, Indianapolis, Indiana, USA
CLINICAL HISTORY AND IMAGING STUDIES
A 55-year-old woman presented with bilateral hip and rib pain. A chest radiograph revealed multiple bilateral rib fractures with callus formation. Insufficiency fractures of the right superior and inferior pubic rami and ischium and possibly of the sacrum were noted on hip and pelvic radiographs, and a subsequent MRI showed avascular necrosis of the left femoral head. Laboratory studies demonstrating hypophosphatemia, in combination with the patient's clinical presentation of osteomalacia, prompted further investigation for the underlying cause.
A parathyroid scan, an octreotide body scan, and a whole body sestamibi scan all revealed normal results with no evidence of neoplasm. The patient's diagnosis of avascular necrosis in combination with pain refractory to non-operative measures resulted in a left total hip arthroplasty.
The patient was lost to follow up until six years later when she presented with bilateral weakness and shooting pains in her legs after a recent fall. She denied back pain and bowel or bladder dysfunction. The work-up included a full body positron emission tomography/computed tomography (PET/CT), which revealed a 4.3 1.7 cm fluoro-deoxyglucose (FDG18)-avid expansile lytic lesion involving the left posterior T12 neural arch. At that time the patient's serum fibroblast growth factor-23 (FGF-23) level was found to be elevated. Subsequently, an MRI of the spine was performed. Sagittal (Figure 1) and axial (Figure 2) T2-weighted, unenhanced and axial T1-weighted, contrast-enhanced, fat-suppressed (Figure 3) images revealed a multi-lobulated, vividly enhancing, heterogeneous mass centered in the left pedicle and laminae of T12, with extension into the epidural space (thick arrows) and posterior paraspinal musculature (thin arrows). The patient underwent T11 to L1 laminectomies and tumor resection.
GROSS AND MICROSCOPIC PATHOLOGY
The gross specimen consisted of multiple fragments of soft tissue and attached bone. The cut surfaces were crunchy and showed areas of focal hemorrhage and cystic degeneration. Histologic examination revealed a fairly well circumscribed, partially encapsulated (Figure 4), moderately cellular tumor with heterogeneous composition (Figure 5). The tumor contained variably sized cystic spaces including large dilated ones filled with blood (Figure 6). The tumor cells appeared spindled with normochromatic, small nuclei and indistinct nucleoli (Figure 7). There was no significant nuclear atypia and mitoses were difficult to find. The tumor cells were focally embedded in a myxochondroid and osteoid-like matrix (Figures 8 and 9) with scattered areas of dystrophic calcification (Figure 8). Peripheral foci of ossification were also noted (Figure 10). The tumor was penetrated by capillary-sized vessels and intermixed with scattered osteoclast-like giant cells (Figure 11). Bone invasion was focally present (Figure 12).