HPV-Related Multiphenotypic Sinonasal Carcinoma with Unusual Palisading Spindle Cell Morphology

Abstract

Human papilloma virus (HPV)-related Multiphenotypic Sinonasal carcinoma (HMSC), formerly known as HPV- related Carcinoma with Adenoid Cystic Carcinoma-Like Features, is a newly described entity occurring exclusively in the sinonasal tract. It is a type of HPV-related sinonasal carcinoma displaying salivary carcinoma-like morphol- ogy (especially adenoid cystic carcinoma). It has strong association with high-risk HPV (particularly HPV type 33). Many histologic patterns have been reported in the literature, including solid, cribriform, and tubular growth pat- terns, myoepithelial and plasmacytoid pattern, spindle and sarcomatoid pattern, and glomeruloid growth pattern. Here, we report a case of HMSC with unusual palisading spindle cell morphology. The patient is a 53-year-old woman with a history of nasal obstruction and drainage. A CT scan showed a soft tissue mass in the right nasal cavity with significant deviation of the septum. The patient subsequently received a right sided anterior ethmoidectomy and maxillary antrostomy. Intraoperatively, a fleshy polypoid mass was noted to occlude the nasal airway and push the right middle turbinate and septum. Histologic sections show multiple architectural patterns within the tumor, including cribriform architecture ad- mixed with hyaline globules, tubular/glandular area with biphasic inner ductal and outer myoepithelial elements, small nests with true keratinization and keratin pearls, and palisading spindle cell morphology. Scattered tumor cells show marked nuclear enlargement and nuclear pleomorphism. Multifocal tumor necrosis and increased mi- totic index are identified. Immunohistochemically, the tumor is positive for p63 (diffuse), p40 (diffuse), CAM5.2 (patchy), cytokeratin AE1/AE3, SMA, calponin, S100 and p16 (strong and diffuse, nuclear and cytoplasmic). RNA <i>in situ</i> hybridization for high risk HPV is positive. We report a HMSC with unusual spindle cell morphology. This case highlights the morphological spectrum that can be seen in this rare tumor and the importance for clinicians to be familiar with this entity.