Metastatic Adenocarcinoma of the Prostate to the Brain Initially Suspected as Meningioma by Magnetic Resonance Imaging

Brain metastasis from prostate cancer is rare, occurring in less than 1% of metastatic prostate cancer patients. Brain metastasis can cause edema, neurologic symptoms, and may be misdiagnosed as primary brain tumors on imaging. A 68-year-old male presented to the emergency department complaining of headaches, right-sided weakness, multiple falls, and a 45 pounds of unintentional weight loss. Computerized tomography (CT) scan without contrast of the head showed a 3.2 cm right frontal mass with edema suspicious for meningioma. Associated nonspecific bony lesions were found on CT of the abdomen and pelvis. Magnetic resonance imaging (MRI) of the brain showed a 2.8 cm right frontal mass with an enhanced dural tail. Preoperative labs were noteworthy for a hemoglobin of 9.7 and prostate-specific antigen (PSA) of 66.7 ng/ml. Craniotomy with resection of tumor was performed with a frozen sample diagnosed as meningioma. Permanent pathology with stains were positive for PSA and prostatic-specific acid phosphatase (PSAP), making the diagnosis of metastatic prostate adenocarcinoma. Postoperatively, nuclear bone scan showed uptake in the axial skeleton consistent with metastasis. After the diagnosis of metastatic prostate cancer was made, bicalutamide was administered followed by degarelix with plans to transition to leuprorelin one month later. This is to be followed up by whole brain radiation therapy (WBRT). PSA was 118.53 ng/ml three weeks after craniotomy, but prior to androgen deprivation therapy. Metastatic prostate cancer can present with neurological symptoms most commonly following spread to the axial skeleton and impingement of the spinal cord. Metastasis to the brain is rare and is usually associated with vague symptomatology depending on extent and location of the lesion. While brain metastasis can occur in known prostate cancer patients, this case shows that metastasis can occur prior to any formal prostate cancer diagnosis and can be mistaken for meningioma on imaging and frozen sectioning. Practitioners must be vigilant, and precautions should be taken to rule in metastatic prostate cancer as a possible cause for a brain lesion in patients of the appropriate demographics.