PHOX2B reliably distinguishes neuroblastoma among small round blue cell tumors

Abstract

Aims

Neuroblastoma shows considerable histologic overlap with other small round blue cell tumors. PHOX2B, a transcription factor essential for autonomic nervous system development, has been reported as an immunohistochemical marker for neuroblastoma. The purpose of this study was to validate the specificity and diagnostic utility of PHOX2B for peripheral neuroblastic tumors.

Methods and Results

We evaluated 240 cases (133 in whole-tissue sections; 107 in tissue microarrays), including 76 peripheral neuroblastic tumors [median age 2 years; including 4 adults] and 164 other tumors: 44 Wilms tumors; 20 Ewing sarcomas; 10 each CIC-rearranged round cell sarcomas, poorly differentiated synovial sarcomas, lymphoblastic lymphomas, alveolar rhabdomyosarcomas, embryonal rhabdomyosarcomas, mesenchymal chondrosarcomas, Merkel cell carcinomas, olfactory neuroblastomas, and melanomas; 5 each NUT midline carcinomas and desmoplastic small round cell tumors. Immunohistochemistry for PHOX2B was performed using a rabbit monoclonal antibody. PHOX2B positivity was defined as the presence of nuclear immunoreactivity in ≥5% of cells. PHOX2B was positive in 70 (92%) peripheral neuroblastic tumors, including 68 of 72 (94%) pediatric and 2 of 4 (50%) adult cases. Furthermore, PHOX2B was consistently negative in all non-peripheral neuroblastic tumors, with staining absent in 160 cases and limited in 4 cases.

Conclusion

PHOX2B is a highly sensitive and specific immunohistochemical marker for peripheral neuroblastic tumors including neuroblastoma. PHOX2B reliably distinguishes neuroblastoma from histologic mimics such as Wilms tumor, Ewing sarcoma, and CIC-rearranged round cell sarcoma. PHOX2B negativity in 2 of 4 adult neuroblastoma cases raises the possibility that some adult neuroblastomas are of a different lineage than pediatric cases.

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