neuroendocrine differentiation is demonstrable with such regularity in carcinoids that the diagnosis is not considered tenable in the absence of at least one of the following features : argyrophilia , the demonstration of neuron-specific-enolase or neuropeptides by immunohistochemistry or other techniques , or the demonstration of numerous dense-core membrane-bound granules , usually 150 to 250 nm in diameter , by electron microscopy .
C1709218
neuroendocrine
C0007095
carcinoids