[1195] Does p16 Immunostaining Increase the Detection of Histologically Minute Squamous Cell Carcinoma of the Upper Aerodigestive Tract?

Mark C Mochel, Stacey E Mills, Paul W Read, Asal N Shoushtari, Edward B Stelow. University of Virginia, Charlottesville

Background: Head and neck squamous cell carcinoma (SCC) not infrequently presents with metastatic disease for which no clinically obvious primary malignancy is identified. In such cases, pathologists are often asked to evaluate speculative biopsies of the upper aerodigestive tract for minute primary tumors to help guide surgical and radiation therapy. It has been previously shown that a significant proportion of these primary tumors are from the oropharynx, many secondary to infection by human papillomavirus (HPV). It has also been shown that p16 immunohistochemistry is an excellent surrogate test for HPV-induced SCC. We speculated that p16 immunostaining might assist in the detection of very small HPV-induced SCCs of the oropharynx that might otherwise be overlooked with conventional staining.
Design: Fifty-one patients were identified with head and neck SCC who had undergone biopsies of the upper aerodigestive tract that had been originally interpreted as negative for SCC. All biopsies and palatine tonsil excisions were reviewed. Immunohistochemistry was performed with antibodies to p16 on all tissues. All positive-staining cases were reviewed a second time for small or low-grade lesions.
Results: There were a total of 156 samples from the 51 patients evaluated with p16 immunohistochemistry. Of those, 143 (92%) were negative for p16 (or showed positive staining of normal appearing reticular tonsillar crypt epithelium, as previously described). Ten (6%) showed focal p16 immunoreactivity that correlated with histological changes consistent with low-grade squamous intraepithelial lesions similar to those of the cervix. Three (2%) showed p16 immunoreactivity that correlated with histological changes consistent with SCC in situ. Eight of the low-grade lesions were in patients whose original biopsies were read as entirely negative, while the other two were found in patients who also had intraepithelial lesions seen in other biopsies. Of the cases with SCC in situ, all had been originally diagnosed as atypical or dysplastic.
Conclusions: Immunohistochemical staining with antibodies to p16 did not improve detection of invasive cancer in cases of head and neck SCC of unknown primary. It did reveal occasional, small low-grade intraepithelial lesions that were missed on initial examination. Given the submission of entire palatine tonsils in many cases, these results suggest that some of the small primary malignancies in these cases may have entirely regressed.
Category: Head & Neck

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 152, Monday Morning


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