Figure legends
Figure 1. X-ray study shows an ill-defined expansile lesion of the right acetabulum.
Figure 2. CT images of the pelvis show an expansile lytic lesion of the posterior column of the right acetabulum with breaching of the medial and lateral cortices as well as the articular surface.
Figure 3. MRI axial images of the right hip joint. The lesion shows bland signal (isointense to muscles) on T1W images (A) and intermediate signal on STIR images (B). Mild diffuse enhancement seen in the post contrast images T1W FS (D) in reference to the pre contrast T1W FS (C).
Figure 4. FDG PET/CT shows intensely increased tracer uptake in the expansile right acetabular/iliac osseous lesion.
Figure 5a. Light microscopic examination reveals a tumor characterized by a proliferation of xanthomatous histiocytes with smaller, moderately atypical epithelioid cells. Additionally, a few osteoclast giant cells were noted (yellow arrows) (H&E stain, magnification x100, x400).
Figure 5b. Isolated epithelioid cells were highlighted by keratin immunohistochemistry (H&E stain, x400).