[1120] Identification of Human Papilloma Virus (HPV) in Basaloid Squamous Cell Carcinoma of the Head and Neck and Its Clinicopathologic Significance

RD Chernock, JS Lewis, Jr, SK El-Mofty. Washington University School of Medicine, St Louis, MO

Background: Basaloid squamous cell carcinoma (BSCC) of the head and neck is a rare, clinically aggressive malignancy that has a predilection for the larynx, hypopharynx and oropharynx. The histologic features are distinct from, but often confused with, those of HPV-related oropharyngeal nonkeratinizing squamous cell carcinoma (NKSCC), which has been shown to be associated with a more favorable outcome. The purpose of this study was to determine the prevalence of HPV in oropharyngeal and nonoropharyngeal tumors with true BSCC histology, and to compare their immunohistochemical reactivity to p16 and p53. In addition, the biological significance of HPV positivity in terms of patient survival was explored.
Design: Cases with a diagnosis of BSCC were selected from the Pathology Department files and those meeting Wain's criteria (Hum Pathol 1986) were included. Tumors with NKSCC morphology were excluded. In-situ hybridization for high-risk HPV subtypes and immunohistochemical staining for p16 and p53 were performed. Detailed medical records and follow up information for all patients were reviewed.
Results: Of 27 BSCC cases, 11 (40.7%) were from the oropharynx and 16 (59.3%) from the larynx or hypopharynx. There were no statistically significant differences in stage or gender by site. The average age of the oropharyngeal BSCC patients was younger but the difference was not statistically significant. Nine of the 11 oropharyngeal BSCCs (81.8 %) were HPV positive and 8 (72.7%) were reactive for p16. In contrast, none of the 16 nonoropharyngeal BSCCs were HPV positive and only one (6.3%) stained positively for p16 (p < 0.01). Two oropharyngeal BSCCs were both HPV and p16 negative and stained strongly for p53. All of the 11 HPV positive oropharyngeal tumors were negative or stained weakly for p53. Thirteen of sixteen (81.3%) non-oropharyngeal BSCCs stained strongly for p53 (p <0.01). The overall survival was better for HPV-positive BSCCs by Kaplan-Meier analysis (p < 0.05).
Conclusions: HPV-positive BSCCs are associated with better survival compared to HPV-negative BSCCs. BSCC of the oropharynx is more likely to be HPV-positive than BSCC of the larynx/hypopharynx. HPV positive oropharyngeal BSCC show strong reactivity to p16 and are negative or weakly reactive to p53. These finding suggest that BSCC of the head and neck may be a mixed clinicopathologic variant.
Category: Head & Neck

Monday, March 9, 2009 1:00 PM

Poster Session II # 164, Monday Afternoon