Intracranial meningioma, mimicking brain metastasis on ¹⁸F sodium fluoride bone scan in a case of carcinoma cervix

INTRODUCTION

Radionuclide bone scintigraphy (BS) is a versatile imaging technique for evaluation of both local and systemic bone diseases. It is a survey of skeleton, when performed, detects abnormal osteoblastic activity in affected bones much before patient presents with clinical symptoms. BS is widely accepted as an important imaging modality for staging and follow-up of cancer patients.[12] Occasionally, BS shows nonosseous, soft-tissue lesions in the body due to focal bone-seeking radiotracer accumulation. In the present case of carcinoma cervix, ¹⁸F sodium fluoride (NaF) bone scan localized a focal area of radiotracer uptake in the right posterior parietal region, mimicking brain metastasis.

CASE REPORT

A 65-year-old postmenopausal woman, known case of squamous cell carcinoma cervix, underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy with pelvic lymph node dissection. Histopathological findings revealed nonkeratinizing type squamous cell carcinoma of the cervix with no lymph node invasion. She was treated with local radiotherapy (RT). After 6 months, the patient presented with complaints of low backache, radiating to both lower limbs associated with paresthesia. Considering the clinical symptoms of backache, she was advised to undergo bone scan. ¹⁸F NaF PET CT bone scan image [Figure 1a] and sagittal images [Figure 1b–d] shows post radio therapy osteoporotic changes in lower part of the lumbar spine and sacral region with L-5 vertebral body insufficiency fracture. Images also showed an area of increased radiotracer uptake in the right side of brain posterior parietal region. Initially, the lesion was suspected as brain metastasis; however, on further evaluation in PET-CT images, it was diagnosed as calcified nonaxial meningioma. Subsequently, she was examined with contrast-enhanced CT (CECT) [Figure 2]. The findings in CECT confirmed the lesion as a mildly enhancing extra-axial, well-defined hyperdense lesion with calcification, located in the right parasagittal falx region, causing displacement of the adjacent cortex due to mass effect. Hypodensity was noted in the right parietofrontal region, compressing the right lateral ventricle with mild midline shift to the left side. The final impression of CECT was suggestive of right falcine meningioma, causing mass effect and midline shift with edema in the right parietal region.

Close

Figure 1 ¹⁸F sodium fluoride bone scan image (a), PET, CT and PET CT sagittal images (b-d) shows post radiotherapy changes (yellow arrow shows L-5 vertebral body insufficiency fracture). Red arrow mark shows non osseous intracranial area of increased ¹⁸F sodium fluoride uptake in the right posterior parietal region

Export to PPT

Close

Figure 2 Brain CE CT, transaxial image shows a calcified falcine meningioma in the right posterior parietal region with mass effect and edema in adjacent tissue corresponding to the ¹⁸F sodium fluoride bone scan, non osseous, intra cranial radiotracer uptake site

Export to PPT

DISCUSSION

In early 1970, easy availability of technetium labeled radiopharmaceuticals for bone imaging surpassed the popularity of ¹⁸F NaF bone scan.[34] Since then, ^99mTc methylene diphosphonate (MDP) BS has been playing important role in diagnosis and management of various benign and malignant bone diseases.[56] It is widely available, simple, and easy to perform test which detects bone lesions 6–12 months earlier than structural imaging modalities. With the availability of PET-CT scanners and medical cyclotrons, ¹⁸F NaF PET-CT bone scan has regained attention and many centers are now routinely performing this test for metastatic workup in cancer patients. ¹⁸F NaF PET-CT has clinical advantage over conventional ^99mTc MDP BS as it provides comprehensive functional and structural details in single test.[7]

Occasionally, ^99mTc MDP BS and ¹⁸F NaF scans show sites of abnormal radiotracer uptake in soft tissue. These lesions can be benign or malignant. The possible factors for increased soft-tissue uptake of bone-seeking radiotracer result from increased extracellular fluid expansion, vascularity, and high regional availability of calcium and phosphate salt leaked in the extracellular space from hypoxic or dead cells.[8]

Bone-seeking radiopharmaceuticals can accumulate in intracranial lesions due to both benign and malignant etiologies which include brain stroke, tumors, and metastatic lesions.[9] In this case of carcinoma cervix, ¹⁸F NaF scan detected focal uptake in an intracranial lesion. Carcinoma cervix is a gynecological malignancy that rarely causes brain metastasis. There are few case reports documenting brain metastasis in patients with aggressive type of carcinoma cervix.[10] In the present case, initially, this lesion was suspected as brain metastasis; however, later on, when the images were examined in detail with both PET-CT and separately with CECT, it was diagnosed as falcine meningioma.

Meningioma is a common intracranial benign tumor, with twice incidence in females. The reported risk factors for meningioma include trauma, hormone replacement therapy, and breast cancer.[11] In many patients, they are silent and are diagnosed as incidental finding on CT or magnetic resonance imaging. About 25% of the meningiomas show calcification and can be visualized on radionuclide bone scan as an incidental finding as seen in the present case.[12]

CONCLUSION

¹⁸F NaF PET-CT scan is a highly sensitive and specific test for detection of osseous lesions in the body. There is no association of meningioma with carcinoma cervix, and it is a rare coincidental finding as seen in the present case. Reading bone scan in such cases indicates that all pathological observations may not always be associated with primary disease but may be synchronous soft-tissue abnormalities of benign or malignant etiologies mimicking a metastatic lesion.