case_images: PMC6180828_01
case_images: MRI of the pelvis. (a) Axial T
  1 weighted image showing a 21-mm round, homogeneous lesion of low signal intensity interforaminally in the left S2 segment of the sacrum. (b) Axial short tau inversion-recovery image showing a well-defined lesion with inhomogeneous signal intensity throughout the lesion with high peripheral rim intensity. (c) Axial T
  1 image with fat saturation after contrast media injection showing moderate enhancement throughout the lesion and in the peripheral rim.
case_images: bjrcr.20150204.g001.jpg
case_images: PMC6180828_01_bjrcr.20150204.g001.jpg
case_images: f1
case_images: The axial short tau inversion-recovery image showed a well-defined lesion with an inhomogeneous signal intensity throughout the lesion with high peripheral rim intensity. The axial T 1 image with fat saturation after contrast media injection showed moderate enhancement throughout the lesion and in the peripheral rim (Figure 1).
case_images: PET-CT scan showing a well-defined sclerotic lesion with mild fludeoxyglucose avidity (average standardized value 2.5) in the S2 segment. No other abnormalities were found on PET-CT scan. PET, positron emission tomography.
case_images: bjrcr.20150204.g002.jpg
case_images: PMC6180828_01_bjrcr.20150204.g002.jpg
case_images: f2
case_images: For further characterization, and in the search of a potential primary tumour, positron emission tomography (PET)-CT was performed, which showed a well-defined sclerotic lesion with mild fludeoxyglucose (FDG) avidity (average standardized value 2.5) in the S2 segment and no other abnormalities (Figure 2).
case_images: Histopathological images. (a) An infiltration of the otherwise normal bone marrow with scattered small groups of big foamy cells. (b) Immunohistochemistry shows lesional cells expressing S100 protein, indicative of fatty infiltration. (c) The cells contain multiple lipid droplets and numerous large mitochondria, shown with antimitochondrial marker.
case_images: bjrcr.20150204.g003.jpg
case_images: PMC6180828_01_bjrcr.20150204.g003.jpg
case_images: f3
case_images: Infiltration of the otherwise normal bone marrow with scattered small groups of big foamy cells was identified (Figure 3a). The cells were negative for cytokeratin AE1/AE3, CD68, barchyury, Melan A, HMB 45, desmin and smooth muscle actin but positive for S100 protein (Figure 3b). The cells contained multiple lipid droplets and numerous large mitochondria; the existence of the latter was exhibited with antimitochondrial marker (Figure 3c).