P01 * AN UNUSUAL CASE OF A METASTATIC ADENOCARCINOMA OF THE PROSTATE INTO AN INTRACRANIAL MENINGIOMA

Abstract

INTRODUCTION: Tumour to tumour metastatis is an unusual but well recognized phenomenon. We present a rare case of a metastatic prostatic adenocarcinoma into a meningioma. METHOD: A 58 year old right handed gentleman was referred to our neuro-oncology service. He reported a history of progressive headache spanning several months but only sought medical attention when he developed focal upper limb seizures and episodic speech arrest. Computed tomography (CT) revealed a left parafalcine lesion. He was started on dexamethasone and went on to have a magnetic resonance imaging (MRI) brain and staging CT. This confirmed disseminated lymphadenopathy and supraclavicular lymph node biopsy diagnosed metastatic prostatic adenocarcinoma, which correlated with elevated prostate specific antigen (PSA). He was started on Degarelix. Pre operative MRI showed a significant reduction in the size of the lesion. This may be due to response to Degarelix or dexamethasone or both. RESULTS: Histology revealed two different populations, an atypical component of small cells positive for PSA, PSAP, CKAE1/AE3 and negative for EMA, vimentin and progesterone receptor thus consistent with a metastatic prostatic adenocarcinoma. Additionally, there were uniform cells with oval and bland nuclei. This component was positive for EMA, vimentin, progesterone receptor and CD56 and negative for CKAE1/AE3 and prostatic markers, consistent with a WHO grade 1 meningothelial meningioma. CONCLUSION: We present a rare phenomenon of metastatic prostatic carcinoma into a meningioma. Interestingly, the tumour showed a marked reduction in size on pre-operative imaging. This is likely due to a response of the metastatic component to anti androgen and steroid therapy.