Neuroblastomas are positive for several neural-related markers, including NSE, synaptophysin, chromogranin (shown here), neurofilament, CD56, peripherin, PGP9.5, secretogranin II, and vasoactive intestinal peptide. A recently described marker Trk receptor protein is associated with favorable histology. In most cases, the diagnosis of neuroblastoma is straightforward based on the aggregate of clinical, laboratory, and routine histologic findings. Immunohistochemical stains usually play an adjunct role. To distinguish undifferentiated neuroblastoma from other small round cell malignancies of childhood, one may need to do a panel consisting of PGP9.5, MIC2 (CD99), desmin, MyoD1, myogenin, and lymphoid markers. S-100 protein immunostain will show putative Schwannian blasts in the thin fibrovascular septa separating the clusters of neuroblastoma cells. Courtesy of: Dr. Luciano de Souza Queiroz, Dept. of Pathology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, São Paulo State, BRAZIL. Additional images are here.