Cytopathologic characteristics and differential diagnostic considerations of neuroglial heterotopia of the retropharyngeal space.

Neuroglial heterotopias (NGH) are rare congenital head and neck lesions composed of differentiated neuroectodermal tissue and representing developmental heterotopias rather than true neoplasms. The case of a male neonate with respiratory distress and early feeding problems depicting a retropharyngeal space mass which in the intraoperative squash smears revealed glial cells with multiple cytoplasmic processes is reported here. Small clusters of cuboidal epithelial cells with rosette-like ependymal structures and cuboidal cells arranged in sheets or branching folds suggestive of choroid plexus cells were also identified. Through this cytological approach a cytologic diagnosis of a NGH or low-grade astrocytoma was suggested. Further evaluation and immunohistochemical studies were conducted on formalin-fixed, paraffin-embedded material. Glial cells, ependymal structures and choroid plexus were identified on H&E sections. Immunohistochemically, the glial cells showed diffuse and strong cytoplasmic staining for glial fibrillary acidic protein (GFAP) and S-100 protein and focal immunoreactivity for synaptophysin and neurofilament. The proliferative index with MIB-1 was around 4%. The diagnosis of NGH of the retropharyngeal space was confirmed based on the clinical, cytopathologic, histopathology, immunohistochemical results, and the location of the tumor. We demonstrated here for the first time the cytopathological features of NGH of the retropharyngeal space with emphasis on differential diagnostic considerations.