P16 Expression Differentiates Merkel Cell Carcinoma.
Alison B Carrigg, Hong Zhang, Yu-Tsueng Liu, Jessica Wang-Rodriguez. University of California San Diego
Background: Immunohistochemistry for p16 has proven useful in the diagnosis of viral driven epithelial malignancies including cervical carcinoma. In the case of cervical cancer, the E6 and E7 proteins of the Human Papilloma Virus (HPV) inactivate Rb and p53 which leads to aberrant cell proliferation and overexpression of p16. It is now known that Merkel Cell Polyomavirus plays a role in cell cycle dysregulation in Merkel cell carcinoma (MCC). To our knowledge, immunohistochemical analysis of p16 in Merkel cell carcinomas has not been investigated. We look to explore the expression of p16 in Merkel cell carcinoma. Additionally, we compare its sensitivity to an immunohistochemical stain for the protein expressed by the integrated Merkel Cell Polyomavirus (MCV) within tumor cells.
Design: Eleven Merkel cell carcinoma cases diagnosed at the VA San Diego Healthcare System over a 21 year period were examined for reactivity to p16 and MCV by immunohistochemistry.
Results: All eleven (100%) positive for p16 in selected tumor cells; however, only 66% of cases stained positive for MCV.
Conclusions: p16 expression in MCC suggests that the oncogenesis of the MCV derived carcinoma uses the inactivation of the Rb pathway similar to that of the HPV. p16 posivitity can be a useful diagnostic tool in differentiating merkel cell carcinoma from other small blue cell tumors. Additional studies to elucidate the incongruity between consistent p16 and variable MCV staining patterns are warranted.
Monday, February 28, 2011 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 69, Monday Morning