Olfactory neuroblastoma with focal ganglioneuroblastic differentiation: a case report with literature review.

Olfactory neuroblastoma (ONB) is a rare malignant neuroectodermal tumour, with clearly defined histologic and immunohistochemical features, that typically arises in the superior nasal cavity. Although the classical clinicopathological features leave little room for misinterpretation, the wide variability in this tumour, including occasional divergent differentiation, may cause diagnostic difficulty. Herein, an unusual case of ONB with focal ganglioneuroblastic differentiation in an 81-year-old woman arising from the anterior ethmoid, filling the upper portion of the left nasal cavity and sparing the sinus cavities, is described. Histologically, the tumour was composed of atypical monotonous round cells that were positive for NSE, CD56, chromogranin, synaptophysin, neurofilament and calretinin and exhibited an irregular lobulated and nested growth pattern and sparse mitotic figures (3 to 4 mitoses per 10 HPF). Focally, the histology changed to ganglioneuroblastic differentiation consisting of large ganglion and spindle cells, positively staining for S-100, GFAP, CD99, neurofilament, calretinin, chromogranin and synaptophysin. Neuroblastomas, occurring in the nasal cavity, in analogy to other sites, tend to have an aggressive biologic behaviour and can histologically mimic other undifferentiated malignant neoplasms of the sinonasal tract. Differential diagnostic problems are discussed; a comprehensive review of the literature has also been performed with a focus on survival.