PMC9891398_01
Lumbar radiographs, anteroposterior view (A) and lateral view (B).. These radiographs were originally interpreted as only showing marginal osteophytes and disc space narrowing at L3-L4, which is best seen on the lateral view (arrow). However, after advanced imaging, it was apparent that there were subtle signs of abnormality that were not identified earlier, including a slight lucency of the sacral alae (*) and disruption of the anterior cortex of the sacrum (arrowhead). These findings are partially obscured by bowel gas in image A and overlapping anatomy of the pelvis in image B.
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FIG1
The radiography report mentioned degenerative changes but did not mention any suspicious findings in the sacral region (Figure 1).
Lumbar spine magnetic resonance imaging, T1-weighted (A) and T2-weighted (B) sagittal views.. There is a large, expansile bone lesion in the sacral ala and bodies S1-S3, which is mildly hypointense on T1 and intermediate signal intensity on T2, with small areas of hyperintensity on the T2-weighted view (B, arrowheads), suggestive of cystic spaces. There is anterior cortical destruction at S2 with soft-tissue penetration into the pre-sacral space (arrow). Also noted is cortical destruction and extension into the sacral spinal canal at the S1 and S2 levels (*).
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FIG2
The patient's lumbar MRI revealed an irregular bone lesion infiltrating the upper sacrum from S1-S3, measuring 6.4 x 4.7 cm on the sagittal view, in addition to evidence of previously identified degenerative changes (Figure 2).
Fluorodeoxyglucose whole-body positron emission tomography/computed tomography.. Increased fluorodeoxyglucose uptake is evident within the sacrum (arrow), with a standardized uptake value of 9.82.
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FIG3
Fluorodeoxyglucose whole-body PET/CT revealed a destructive, hypermetabolic sacral bone lesion with encasement of the sacral canal at the S1-S3 levels, and involvement of the presacral soft tissue (Figure 3).
Axial computed tomography section through the first sacral segment.. This reveals a lytic, expansile mass with soft-tissue attenuation, spanning the sacral body and alae bilaterally, with thinning but no sclerosis of the cortical bone (arrowheads).
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FIG4
The CT scan revealed a large lytic sacral mass with cortical thinning, a non-sclerotic border, and no signs of pathologic fracture (Figure 4).
Hematoxylin and eosin section showing multinucleated giant cells (arrows) with interposed mononuclear cells.. 400x magnification.
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FIG5
Histopathology of the mass revealed an indolent giant cell-rich bone lesion, consisting of abundant osteoclast-like multinucleated giant cells associated with bland-looking spindly fibroblast-like mononuclear cells, young capillaries, and focal stromal hemorrhage, findings typical for GCT (Figure 5).