Cytological diagnosis of olfactory neuroblastoma at metastatic sites, with emphasis on role of insulinoma-associated protein 1 immunocytochemistry.

Metatstatic ONB can resemble other small round cell tumors, as all the diagnostic features of ONB may not be readily evident. INSM1 immunocytochemistry has high sensitivity and specificity and can reliably be used as a single marker to support the cytomorphology for a confirmatory diagnosis of ONB, even on direct smears if a cell block is not available.