Biphasic low-grade nasopharyngeal papillary adenocarcinoma with a prominent spindle cell component: report of a case localized to the posterior nasal septum.

A case (female, 39 years of) of thyroid-like nasopharyngeal low-grade papillary adenocarcinoma with a significant spindle cell component is presented. The tumor was located on the posterior nasal septum. The spindle cells displayed nuclear features very much similar to the epithelial component and the two cell types merged imperceptibly. Immunohistochemically, the neoplastic cells (including the spindle cell component) were strongly and diffusely positive for TTF-1, cytokeratins (AE1-3), cytokeratin 19 and vimentin. C-kit immunohistochemistry showed diffuse mild to moderate membranous positivity with focal areas displaying moderate to strong immunoreactivity. EMA was strongly positive in the epithelial component with membranous and cytoplasmic reactivity whereas the spindle cell component was weakly although diffusely positive. Carcinoembryonic antigen, calcitonin, chromogranin A, S100-protein, thyroglobulin, cdx2 and p63 were negative. The proliferative activity (Mib-1/Ki-67) was low; 3-4%. In the molecular genetic study we found no mutations at position 1799 (exon 15) in the BRAF-gene, (BRAFV600E) or in exons 9 and 11 of the KIT-gene.