SYP and small cell lung carcinoma: Evidence of “neuroendocrine” differentiation includes the presence of dense core secretory granules in SCLC cells, with similar ultrastructure to those in Kulchitsky cells; indeed the co-expression of such neurendocrine markers as synaptophysin, chromogranin A and CD56 [4] assists in the immunohistochemical (IHC) diagnosis of SCLC.