Cavernous Hemangioma of the Ilium Mimicking Aggressive Malignant Bone Tumor with Increased Activity on 18F-FDG PET/CT
A 22-year-old female presented with a gradually increasing pelvic mass with tenderness for 1 month. There was no evidence of previous trauma or fever, and also there was no history of other medical or surgical disease and no evidence of pregnancy. On the physical examination, there was a palpable mass with tenderness in her left pelvic area. A plain radiograph of the pelvis showed a huge, geographic osteolytic lesion with a thick and irregular sclerotic rim in the left ilium (). CT showed an ill marginated, 13 × 10 cm, osteolytic lesion of the left ilium with extraosseous soft tissue mass formation and intralesional stippled calcifications. On the contrast-enhanced CT, the mass showed irregular, rim enhancement and focal enhanced soft tissue components (). On MRI, the lesion had a heterogeneous intermediate signal on the T1-weighted images, a heterogeneous high signal on fat suppressed T2-weighted images, and irregular low signal septa on T1 and T2-weighted images. After enhancement with gadolinium, the mass was demonstrated as a heterogeneously enhanced mass, as well as non-enhanced soft tissue components and septal structures (). On 99mTc hydroxymethane diphosphonate (HDP) bone scintigraphy, increased isotope uptake was depicted in the left iliac bone (). After fasting for 6 hours, intravenous injection of 375 MBq of 18F-FDG was performed (at that time, her blood glucose level was 92 mg/dL). The PET scan (3 min/bed, 6-8 beds) was obtained from 60 minutes post 18F-FDG injection. 18F-FDG PET/CT scanning was done by Discovery PET/CT scanner (GE Healthcare, Milwaukee, WI, USA), and scans were acquired in 3D mode. Reconstruction was done by ordered subset expectation maximization (OSEM) (128 × 128 matrix, 3.27 mm slice thickness, subsets: 21, iteration: 2, post-Filter: 5.14 FWHM (mm), loop-Filter: 4.69 FWHM, diameter: 60 cm) after attenuation correction. 18F-FDG PET/CT demonstrated heterogeneous 18F-FDG uptakes, which had low and high 18F-FDG uptake (maximum standard uptake value [SUVmax] = 5.1) within the mass (). Based on the imaging features, chondrogenic malignant bone tumor in the ilium was considered even though, when taking her age into account, it was unusual. Complete removal of the tumor was performed. On gross examination, the mass appeared as a vascular mass containing central necrosis, irregular bony septa, and fibrous tissues. Histopathologic examination of the excised mass showed bony trabeculae with dilated vascular spaces filled with blood and endothelial lining (), and it was confirmed as cavernous hemangioma of the ilium by the experienced musculoskeletal pathologists.