Review of the cytological features of olfactory neuroblastoma: A retrospective single‐center study

Abstract

Olfactory neuroblastoma (ONB) is a rare malignant neuroectodermal tumor. Due to the rarity, there are scarce reports describing the cytological features of ONB. Thus, we aimed to analyze these cytological features and discuss their differences depending on the histological grading of ONB. Patients with a histopathological diagnosis of ONB who underwent fine‐needle aspiration cytology were enrolled in the study. The cytological features, including arrangement and shape of neoplastic cells, nuclear features, and presence of rosettes, were analyzed. Eight patients with ONB were enrolled; cytological specimens of seven patients were obtained from metastatic lesions and that of one patient were obtained from the nasal cavity tumor. The cytological specimens demonstrated variable‐sized clusters of neoplastic cells and single cells. Two‐cell pattern, composed of large‐sized viable neoplastic cells and small‐sized apoptotic cells, was noted in 3 of 4 high‐grade ONBs but in none of 4 low‐grade ONBs. This reflects that the presence of the two‐cell pattern may represent higher proliferation in neoplastic cells. The neoplastic cells had scant cytoplasm and round to oval nuclei containing fine to granular chromatin without conspicuous nucleoli. Rosettes and paranuclear blue bodies were observed in one patient. Most cytological specimens of ONB were obtained from metastatic lesions, especially from the cervical lymph node. Thus, ONB should be differentiated from malignant lymphoma and small cell neuroendocrine carcinoma. Recognition of these cytological features of ONB while considering patient history can aid in correctly diagnosing ONBs. Moreover, the presence of two‐cell pattern might reflect high‐grade histology of ONB.

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

“…A two-cell pattern of viable and apoptotic cells described in some ONBs and found to correlate with high tumor grade is also a non-specific finding reflective of high proliferation of tumor cells, and has been reported in other tumors of neuroendocrine/neuroectodermal origin in the head and neck. 5 We identified this feature in half the aspirates in our study, and found no correlation with Hyams grade. Another noteworthy documented feature is 'paranuclear blue bodies' which are dark blue cytoplasmic globules indenting the nucleus, initially described in small cell carcinoma and subsequently in other small round cell tumors like ONB.…”

“…Another noteworthy documented feature is 'paranuclear blue bodies' which are dark blue cytoplasmic globules indenting the nucleus, initially described in small cell carcinoma and subsequently in other small round cell tumors like ONB. 5 However, we did not identify them in any of the cases in this series. Mitotic fig-…”

“…4,5 However, these are merely suggestive, but not pathognomonic of a diagnosis of ONB, since they are also seen in other neuroendocrine and other small round cell tumors. 4,5 Mahooti et al found that identification of background neuropil along with rosettes is critical in rendering a diagnosis of ONB on aspirates. 12 However, the caveat is that this finding, although specific, is not unequivocally present in all ONB aspirates, as also seen in our study.…”

“…However, the description of cytological features of ONB in literature is limited, with only four case series and a few isolated reports. 4,5 Without a knowledge of the cytomorphology, recognition of ONB on FNAC at metastatic sites can be difficult, especially if relevant clinical history is not available. We recently described our experience with metastases to the parotid, which included an FNAC from a case of metastatic ONB.…”

“…The primary site of ONB is relatively inaccessible for sampling by fine needle aspiration; however, metastatic sites present opportunities for direct as well as image‐guided fine needle aspiration cytology (FNAC) diagnosis, both at presentation and later during the disease. However, the description of cytological features of ONB in literature is limited, with only four case series and a few isolated reports 4,5 . Without a knowledge of the cytomorphology, recognition of ONB on FNAC at metastatic sites can be difficult, especially if relevant clinical history is not available.…”