CD81 and neoplasm: From the phenotypic point of view, tumor cells from all neuroblastic tumors investigated (38 NBL, 4 ganglioneuroblastomas, 1 ganglioneuroma, and 1 pheochromocytoma) except 1 (43/44, 98%) showed a rather homogenous phenotype with systematic positivity for CD56++, GD2++, CD90+, CD9++, and CD81++ while they lacked expression of CD99, EpCAM, CD10, nuMyoD1, and numyogenin.