Brain metastasis from small-cell neuroendocrine carcinoma of the urinary bladder: a case report

Eight months after radical surgery for small-cell neuroendocrine carcinoma (SCNC) of the urinary bladder, a 69-year-old man was admitted with a brain tumor in the left frontal lobe. The tumor, about 5 cm in diameter, was intensely but heterogeneously enhanced on computed tomography and magnetic resonance imaging. The tumor was subtotally removed, leaving only the portion adjacent to the anterior horn of the left lateral ventricle. Microscopically, the tumor was composed of diffuse sheets of small tumor cells with round to spindle-shaped nuclei, indistinct nucleoli, scant or absent cytoplasm, and indistinct cell margins. Immunohistochemically, the tumor cells were positive for synaptophysin, neuron-specific enolase, chromogranin A, and keratin. Ultrastructurally, the tumor cells showed classic neurosecretory granules and microvilli in the cytoplasm. The tumor was diagnosed as a brain metastasis from SCNC of the urinary bladder. After surgery, whole-brain radiation therapy of 40 Gy was performed, which succeeded in controlling the residual tumor. However, 4 months after surgery, the patient died of meningeal carcinomatosis. To our knowledge, this is the first report focusing on brain metastasis from SCNC of the urinary bladder. The clinicopathological features and pathological diagnosis of this tumor are discussed.