Olfactory Carcinoma (OCA): Report of Two Examples of a Rare, Clinically Aggressive, Sinonasal Malignancy with Neuroepithelial Differentiation.

Introduction

Sinonasal neuroendocrine malignancies are subclassified into small cell and large cell neuroendocrine carcinoma and olfactory neuroblastoma (ONB). Recently, neoplasms that display histomorphologic similarities to ONB but additionally reveal overt epithelial features have been designated as olfactory carcinoma (OCA). Herein, we report the clinicopathologic characteristics of two cases of OCA.

Material and methods

The archives of the OSU Department of Pathology were searched for tumors diagnosed as or displaying features suggestive of OCA. Information regarding patient age and gender, location, radiographic, histopathologic and immunohistochemical features of the lesion, treatment and follow-up was retrieved.

Results

Two cases, arising in 48 and 55-year-old males, met the diagnostic criteria for OCA. Both presented as destructive, midline, sinonasal tumors (4.3 and 7.0cm) that caused erosion of the cribriform plate and nasal septum, extending into the ethmoid, sphenoid and maxillary sinuses, with intracranial and, in one case, orbital involvement. Histopathologically, the tumors exhibited solid or ribbon-like areas with prominent rosette formation, or organoid and trabecular arrangements lacking identifiable neural-type rosettes. Neoplastic cells were small with rounded, ovoid and/or angulated, hyperchromatic nuclei, coarse nucleoplasm, nuclear molding, and minimal cytoplasm with indistinct cell borders. Geographic necrosis, apoptosis and mitoses were plentiful. Immunohistochemically, lesional cells featured focal-to-diffuse reactivity for pancytokeratin, CAM 5.2, EMA and p40, in addition to variable positivity for synaptophysin, chromogranin, CD56 and INSM1. S100 focally highlighted sustentacular cells, while SMARCB1 expression was retained. Both tumors were classified as Stage IVb and treated with surgery and chemoradiation therapy. Patients remained disease-free after 7 and 60 months of follow-up.

Conclusions

OCAs are exceedingly rare sinonasal malignancies with aggressive biologic behavior and overt neuroepithelial attributes. Such diagnosis, however, may be challenging due to lack of well-established criteria and occasional absence of glandular or rosette-like structures. Therefore, proper diagnosis relies heavily on immunohistochemical recognition of the combined neuroepithelial differentiation.