[1255] Strong P16 Expression Associates with Invasion of the Vulvar Extramammary Paget's Disease

Gloria Zhang, Yun Zhao, Jennifer A Brainard, Fadi W Abdul-Karim, Bin Yang. Cleveland Clinic, Cleveland, OH; Peking University People Hospital, Beijing, China

Background: Vulvar extramammary Paget's disease (VEMPD) is a rare vulvar neoplasm which can be histopathologically mistaken as vulvar intraepithelial neoplasia (VIN). P16, as a surrogate biomarker for HPV-related squamous dysplasia, has been applied to facilitate differential diagnoses between classic VIN and other vulvar lesions such as VEMPD. However, the expression pattern of p16 in VEMPD has not been reported. We studied the expression of p16 protein immunohistochemically in 40 cases of VEMPD.
Design: A cohort of 40 cases of VEMPD was searched and retrieved from our hospital archive. Clinicopathologic data was reviewed and tabulated. P16 immunostaining was performed on recuts of all cases. P16 immunostaining pattern was categorized as negative, focal or continuous. Focal pattern is defined as patch and discontinuous staining in less than 30% of cells with weak staining intensity. Continuous pattern is defined as diffuse staining of >90% cells of Pagetoid tumor cells with strong staining intensity.
Results: p16 expression was seen in 36/40 (90%) of VEMPD. Four cases (10%) of VEMPD showed negative p16 staining. Focal p16 staining pattern was observed in 20 (50%) cases. Continuous staining pattern was seen in 16 (40%) cases. VEMPD with dermal invasion, ranging from microinvasion to large nodular mass, was identified in 5 (12.5%) cases. Interestingly, all 5 VEMPD cases with invasion had continuous staining pattern. About 31% (5/16) of VEMPD with continuous p16 staining pattern associated with invasion. In contrast, none of the 24 VEMPD cases with either negative p16 or focal p16 staining pattern was associated with dermal invasion.
Conclusions: We have found that p16 protein is expressed in a vast majority (90%) of VEMPD. Strong and continuous p16 immunostaining pattern is associated with invasive VEMPD. Given overexpression of p16 seen in both VEMPD and usual/classic VIN, p16 immunostaining is not useful in differentiating VEMPD from usual/classic VIN. Our data indicates that p16 tumor suppressor gene is likely involved in the pathogenesis of VEMPD and a continuous pattern of p16 immunostaining may be linked to invasion.
Category: Gynecologic & Obstetrics

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 187, Monday Morning


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