Utility of Phox2b Immunohistochemical Stain in Neural Crest Tumors and Non-neural Crest Tumors in Pediatric Patients

Abstract

Background

This study evaluated the utility of Phox2b in pediatric tumors. Previously tyrosine hydroxylase (TH) was the most widely utilized sympathoadrenal marker specific for neural crest tumors with neuronal/neuroendocrine differentiation. However, its sensitivity is insufficient. Recently Phox2b has emerged as another specific marker for this entity.

Methods

Phox2b IHC was performed on 159 pediatric tumors including (1) 65 neural crest tumors with neuronal differentiation [peripheral neuroblastic tumors (pNT)]: 15 neuroblastoma undifferentiated (NB-UD), 10 NB poorly differentiated (NB-PD), 10 NB differentiating (NB-D), 10 ganglioneuroblastoma intermixed (GNBi), 10 GNB nodular (GNBn), and 10 ganglioneuroma (GN); (2) 23 neural crest tumors with neuroendocrine differentiation [pheochromocytoma/paraganglioma (PCC/PG)]; (3) 27 other neural crest tumors including one composite rhabdomyosarcoma/neuroblastoma; and (4) 44 non-neural crest tumors. TH IHC was performed on group (1), (2) and (3).

Results

Phox2b was diffusely expressed in pNT (n=65/65): strongly in NB-UD and NB-PD, and in NB-D, GNB and GN with less intensity. Diffuse TH was seen in all NB-PD, NB-D, GNB and GN, but 9/15 NB-UD and a nodule in GNBn didn't express TH (n=55/65). PCC/PG expressed diffuse Phox2b (n=23/23) and diffuse TH except for one tumor (n=22/23). In composite rhabdomyosarcoma, TH was expressed only in neuroblastic cells and Phox2b was diffusely positive in neuroblastic cells and focally in rhabdomyosarcoma. All other tumors were negative for Phox2b (n=0/44).

Conclusion

Phox2b was a specific and sensitive marker for pNT and PCC/PG, especially useful for identifying NB-UD often lacked TH. Our study also presented a composite rhabdomyosarcoma/neuroblastoma of neural-crest origin.

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