Atypical Hemangioma Mimicking Metastasis on 18F-Sodium Fluoride Positron Emission Tomography-Computed Tomography and Magnetic Resonance Imaging: Gallium-68-Prostate-Specific Membrane Antigen Positron Emission Tomography Improves the Specificity of Bone Lesions

A 66-year-old man has high-risk prostate cancer with Gleason score (4+5). 18F-sodium fluoride positron emission tomography-computed tomography (¹⁸F-NaF PET-CT) performed after injection of 6.7 mCi of ¹⁸F-NaF for staging [Figure 1].¹⁸F-NaF PET-CT showed solitary osteoblastic lesion at the body of D4 vertebra. Magnetic resonance imaging showed features of atypical hemangioma; however metastasis cannot be ruled out [Figure 2]. To rule out bone metastasis, gallium-68-prostate-specific membrane antigen (Ga-68 PSMA) PET-CT is performed which shows no abnormal lesion. Eight-month follow-up by ¹⁸F-NaF PET-CT showed persistent osteoblastic lesion at D4 without any significant change thus, confirming the initial diagnosis of atypical hemangioma [Figure 3].

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Figure 1 (a) Positron emission tomography sodium fluoride maximum intensity projection images, (b) coronal and transaxial sodium fluoride positron emission tomography images showing focal area of increased radiotracer activity in body of D4 vertebra, noncontrast computed tomography component showing sclerotic lesion

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Figure 2 (a) Magnetic resonance imaging T1-weighted transaxial, saggital images showing hypointense marrow over D4 vertebra. (b) T2-weighted transaxial, sagittal images showing hyperintense lesion, predominantly along the periphery, with marginal contrast uptake. No associated soft tissue component noted. Findings suggestive of atypical hemangioma, however, metastasis cannot be ruled out

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Figure 3 (a) Maximum intensity projection images of gallium-68-prostate-specific membrane antigen. (b and c) Transaxial, sagittal gallium-68-prostate-specific membrane antigen positron emission tomography and fused positron emission tomography-computed tomography images do not show any abnormal uptake. (d and e) 8-month follow-up maximum intensity projection and fused sagittal images of 18F-sodium fluoride positron emission tomography-computed tomography showing persistent osteoblastic bone lesion at the body of D4 with no time interval change noted

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Hemangioma is one of the most common benign tumors of the spine, with a reported prevalence of 10%–12%.[1] Vertebral hemangiomas develop most frequently in the thoracic spine followed by the lumbar spine.[2] Hemangiomas in the vertebrae cause rarefaction with exaggerated vertical coarse striations. This appearance has been described on radiographs and CT as “polka-dot,” “honeycomb,” “corduroy cloth,” “jail bar,” and “salt and pepper,” with a decrease in the overall density of the vertebral body due to the presence of fatty marrow.[3] At scintigraphy, the appearance of osseous hemangiomas ranges from photopenia to a moderate increase in radiotracer uptake.

Magnetic resonance imaging (MRI) features largely depend on the proportion of fat and vascularity of the lesions. T1-weighted MRI has areas of high-signal intensity due to high-fat content, while T2-weighted images of high-signal intensity typically correspond to the vascularity of hemangiomas.[4] Atypical hemangiomas, which may vary in appearance, include those that are hypointense on T1-weighted images but retain the typical characteristics on T2-weighted and fat-suppressed postcontrast images.[5] This appearance may resemble a metastatic lesion, which also has low signal on T1-weighted and high signal on T2-weighted images.[6] The signal intensities of atypical hemangiomas can be indeterminate, but the morphology of the lesion, including the presence of coarse trabeculae, can be used to make the diagnosis. For indeterminate cases, CT can be used as CTs are more sensitive to the characteristic osseous remodeling of hemangiomas than MRI. If necessary, follow-up examinations can be performed to ensure stability.

¹⁸F-NaF PET-CT is a sensitive tool for detecting skeletal metastases.[78] Ga-68 PSMA is a promising tracer for both staging and detection of biochemical recurrence in prostate cancer.[9] Preliminary data indicate that the detection rate of Ga-68 PSMA PET-CT is clearly superior to the planar bone scan in the detection of osseous metastasis;[10] however, a direct comparison with ^99mTc-SPECT/CT or ¹⁸F-NaF PET-CT may be useful to assess the superiority of Ga-68 PSMA over bone scan. We report our experience regarding the value of Ga-68 PSMA in diagnosis, characterization, and differentiation of atypical hemangioma from spinal metastasis. The atypical and typical hemangiomas may not express PSMA and do not show increased tracer uptake, while the metastases from prostate showed increased tracer uptake, suggestive of PSMA expression. Therefore, Ga-68 PSMA could be suggested as an effective complementary imaging method to MRI, particularly for enhancing diagnostic specificity.