Fine needle aspiration cytology of metastatic olfactory neuroblastoma

Olfactory neuroblastoma (ONB) is an uncommon malignant neoplasm that originates in the upper nasal cavity. Cytomorphologic descriptions of ONB have been limited to isolated case reports. The features of a series of metastatic ONB diagnosed by fine needle aspiration (FNA) are described.

Cytologic findings in four patients with ONB metastatic to cervical lymph nodes who underwent FNA were reviewed, and the cytomorphologic findings were summarized. Immunocytochemical findings and ultrastructural features with selected immunoelectron microscopy from three cases are described.

Aspiration cytology revealed a predominance of single cells with intermixed small, loosely cohesive, three-dimensional cell groups. Cell size was small to intermediate, with round nuclei. There was an overall monomorphic appearance, with minimal nuclear pleomorphism. Chromatin was finely granular and stippled, with multiple, small chromocenters. Cytoplasm in the cell groups had a fibrillary quality and was moderate in amount. Single nuclei were frequently stripped of cytoplasm. Occasional pseudorosettes were noted. Immunocytochemical stains were positive for both neuronspecific enolase and synaptophysin. Ultrastructural examination showed neuritic cell processes with neurosecretory granules and microtubules. Immunoelectron microscopy showed positive labeling of neurosecretory granules by chromogranin A.

FNA cytomorphology, in combination with ancillary studies, can provide an accurate diagnosis of metastatic ONB.