RARE-17NEUROENDOCRINE CARCINOMA IN THE BRAIN

OBJECT: Neuroendocrine carcinoma (NEC) is a malignant tumor that usually arises in the lung, pancreas and gastrointestinal tract. Brain metastasis of NEC is merely reported. Herein, we report two cases of NEC in the brain mimicking glioblastoma (GBM). CASES: Both patients were in their 60s, cystic lesions with peritumoral edema affected the temporal lobe. Cyst walls were thin but hyperintense in diffusion weighted images implying increased cellularity. Positron emission tomography (PET) revealed malignant nature by strong uptake of methionine (MET), fluorothymidine (FLT) and fluoromisonidazole likewise GBM. However, fluorodeoxyglucose (FDG) indicated relatively weak uptakes compared as GBM. Both tumors were resected under the preoperative diagnosis of GBM, however, pathological diagnoses were NEC by immunohistochemical finding of negative GFAP and positive markers of neuroendocrine differentiation. Systemic examination failed to reveal the origin. Both cases underwent radiotherapy. One case was lost by spinal dissemination 11 months after the operation. DISCUSSION: FDG-PET of neuroendocrine tumor in the extracranial lesion does not always demonstrate strong uptake. FDG-PET for NEC in the brain could be less accumulated than GBM, while it should be evaluated keeping in mind that the background level of FDG would be high in the brain tissue. In case of malignant tumors endorsed by other tracer such as MET and FLT, inconsistent FDG-PET finding might be useful for the diagnosis of NEC in the brain.