[Diagnostic utility of tyrosine hydroxylase in peripheral neuroblastic tumors]

Objective: To investigation the diagnostic utility of tyrosine hydroxylase (TH) immunohistochemically as a marker of peripheral neuroblastic tumors(pNT). Methods: The study included 1 024 cases, 643 primary and metastatic pNT cases, 381 non-pNT cases, including small round cell tumors such as primitive neuroectodermal tumor (PNET), rhabdomyosarcoma, lymphoma, nephroblastoma, as well as other more common tumors (medulloblastoma, hepatoblastoma, pleuropulmonary blastoma, renal clear cell sarcoma, Langerhans cell histiocytosis, lipoblatoma etc). Tissue slides of these 1 024 cases were stained with TH and other common antibodies to evaluate whether TH was useful to identify pNT. Results: TH showed cytoplasmic staining in 100.0% (643/643) of pNT and 3.9% (15/381) of non-pNT. TH expression was seen in some poorly differentiated and undifferentiated tumors with focal or scattered patterns. In some cases, more scattering was seen in neuroblastoma with poor differentiation. The sensitivity, specificity, positive predictive value and negative predictive value of TH was 100.0% (643/643), 96.1%(366/381), 97.7%(643/658) and 100.0% (366/366), respectively. There was no TH expression in the 248 cases of other small round cell tumors (PNET, rhabdomyosarcoma, lymphoma, etc), thus suggesting TH was useful to differentiate between PNET and neuroblastoma. As CD99 was positive in 95% PNET, some PNET would be CD99 negative. In those cases, particularly with diffuse rosettes forming, TH immunostaining would be useful. Conclusion: TH is sensitive and specific for pNT in the differential diagnosis from other tumors of childhood and shows high diagnostic utility.