[1221] Undifferentiated Carcinoma of the Oropharynx Is an HPV-Related Tumor with a Good Prognosis

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

Background: Undifferentiated carcinoma, also termed “undifferentiated carcinoma of the nasopharyngeal type” and “lymphoepithelioma,” is an uncommon and histologically distinct tumor in the oropharynx, which, in Western countries, has been clearly shown not to harbor Epstein Barr virus. However, no study has analyzed these tumors for HPV.
Design: Oropharyngeal tumors with a diagnosis of “undifferentiated carcinoma” were retrieved from the department files from 1989 to 6/2009. After consensus review by all three study pathologists, sixteen were found to have the typical histologic features and to lack distinguishing characteristics of other oropharyngeal malignancies. Of these, 15 had material available for ancillary studies. Immunohistochemistry (IHC) for p16 and p53 and in-situ hybridization (ISH) for HPV were performed on these cases. Cases with positive p16 IHC, but negative HPV-ISH, were analyzed by PCR for high risk HPV types. The results were correlated with pathologic findings and clinical follow up.
Results: The average age was 59.2 years with an average follow up of 3.2 years. Ninety-one percent (91%) were smokers. The majority (13; 81%) were located in the tonsil, with 2 in the base of tongue (13%) and 1 in the soft palate (6%). Thirteen (81%) had nodal metastases. Fourteen of the 15 (93%) showed positive p16 IHC staining, but only 8 of these 14 (57%) were positive for HPV by ISH. PCR was positive in all 6 of these ISH-negative, p16-positive tumors, however, demonstrating that 14 of the 15 (93%) tumors were HPV positive. The p16 negative tumor was strongly p53 positive, as were four p16 positive tumors, and overall, 5 tumors (33%) had strong p53 staining. Three patients had disease recurrence (average 7 months) and two died of disease for an overall disease free survival of 87%. Two year overall and disease specific survival was 73% and 100%. HPV status did not correlate with outcome as most were positive. All three patients with disease recurrence were HPV positive.
Conclusions: The majority of oropharyngeal undifferentiated carcinomas are HPV-related and p16 positive with a low rate of p53 mutation. Disease specific survival is very good and is comparable to the best published rates for HPV-related oropharyngeal carcinomas.
Category: Head & Neck

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 160, Tuesday Afternoon


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