CD99 and NKX2.2 positive neuroblastoma diagnosed on cytology: A potential diagnostic pitfall and necessity of pathological evaluation of the primary site.

Immunohistochemistry plays a vital role in the diagnosis of small round cell tumors. CD99 immunonegativity is one of the features, which helps in distinguishing neuroblastoma from other small round cell tumors. NKX2.2 is a specific marker of Ewing sarcoma, which is a differential for poorly differentiated neuroblastoma. Here, we present a case of metastatic neuroblastoma showing immunoreactivity for both CD99 and NKX2.2 on cytology of the metastatic site causing diagnostic dilemma. Biopsy study of the adrenal lesion revealed presence of differentiating cells and neuropil, highlighting the importance of evaluation of the primary site and limitation of cytology.