Prostate carcinoma mimicking a sphenoid wing meningioma

Spheno-orbital Lesions-A Major Review of Nonmeningioma Causes

PURPOSE

To review the imaging features of the broad range of nonmeningioma lesions of the greater wing of the sphenoid (GWS) bone and adjacent orbit to assist clinicians in differentiating these lesions from each other and from the most common lesion of the GWS and adjacent orbit, meningioma.

METHODS

We reviewed 32 cases of spheno-orbital lesions involving the GWS from our own practice, as well as 109 published cases (total 141), with emphasis on available imaging features on computerized tomography (CT) and MRI. Features that might assist in differentiating meningioma from its mimics were analyzed for each lesion, including the presence of an osteoblastic or hyperostotic response, bone erosion or osteolysis, homogeneous hypo- or hyperintensity on T2-weighted MRI, leptomeningeal involvement, and the absence of a "dural tail" on contrast-enhanced MRI. The clinical and imaging features were also briefly summarized for each diagnostic group.

RESULTS

The largest diagnostic group was metastasis (67 cases, 47.5%). The most useful imaging features that helped differentiate meningioma from its mimics were the presence of bone erosion and the absence of a "dural tail." Other features were helpful in a small minority of cases only. Metastatic prostate cancer was the largest single group (21 cases), and 18 (85.7%) of these were osteoblastic and most closely mimicked meningioma. Prostate cancer patients were generally older than males with GWS meningioma. Almost all other (44/46, or 95.7%) metastatic lesions showed evidence of bone erosion. Almost half (30 of 61, 49.2%) of patients with metastasis presented without a known diagnosis of malignancy. Among children 16 years of age and less, Langerhans cell histiocytosis (10 cases), dermoid cyst (5), and Ewing's sarcoma (5) were the most common diagnoses.

CONCLUSIONS

A combination of a careful history and both CT and MRI gives information, which can best guide the management of patients with spheno-orbital lesions. Metastatic prostate cancer to the GWS most closely mimics GWS meningioma but can in most cases be differentiated on clinical and imaging features. Older males with hyperostotic lesions of the GWS should be investigated for prostate cancer. Other metastatic lesions and primary tumors of the GWS, as well as benign and structural lesions can readily be differentiated from meningioma on clinical and imaging features.

Noninvasive Differentiation of Meningiomas and Dural Metastases Using Intratumoral Vascularity Obtained by Arterial Spin Labeling

PURPOSE

Using conventional magnetic resonance imaging (MRI) techniques, the imaging features of meningiomas and dural metastases overlap and a differentiation between these tumor entities therefore remains difficult, particularly in patients with a known primary neoplasm. The purpose of this study was to explore the potential role of normalized vascular intratumoral signal intensity values (nVITS) obtained from pulsed arterial spin labeling (PASL) to differentiate between meningiomas and dural metastases.

METHODS

In this study PASL was performed in 46 patients with meningiomas (n = 30) and dural metastases (n = 16) on a 3T scanner, in addition to the routine diagnostic imaging protocol. The ratio between the vascular signal intensity of the tumor and the contralateral normal white matter obtained by PASL images was defined as nVITS.

RESULTS

Meningiomas showed significantly higher nVITS values compared to dural metastases (p < 0.001). The optimal nVITS cut-off value to differentiate between the 2 tumor entities was 1.989, with 100% sensitivity and 81.2% specificity.

CONCLUSION

The nVITS values obtained by PASL provide a fast and noninvasive MRI technique with which to differentiate between meningiomas and dural metastases in a routine clinical setting based on tumor vascularity.

Dural Metastases of Advanced Prostate Cancer Detected by 18F-Fluorocholine

Prostate cancer with extensive dural metastases is very rare, with only few cases described in the literature. We report one such case of a 74-year-old man with advanced prostate cancer, and in relatively good clinical condition. The patient returned with complaints of headache and diplopia. Fluorocholine (¹⁸F) chloride (¹⁸F-FCH) is an analog of choline in which a hydrogen atom has been replaced by fluorine (¹⁸F). After crossing the cell membrane by a carrier-mediated mechanism, choline is phosphorylated by choline kinase to produce phosphorylcholine. ¹⁸F-FCH positron emission tomography–computed tomography (PET/CT) is widely used to stage and restage patients affected by prostate cancer with good sensitivity. ¹⁸F-FCH PET/CT showed disease progression with the onset of multiple skull lesions. Numerous suspicious dural hypermetabolic lesions indicating neoplastic involvement were detected along the fronto-parietal convexities, in the left fronto-orbital region and right lateral wall of the orbit, concerning for metastases in these regions. A contrast-enhanced computed tomography (CECT) scan was performed which showed corresponding enhancing tissue which correlated with the PET findings. The final imaging diagnosis was osteo-dural metastases from prostate cancer associated with poor outcome. Awareness of this pattern of metastases may be of clinical relevance in order to avoid unnecessary invasive diagnostic procedures in groups of patients with a dismal prognosis.