[723] “Basal Cell Carcinoma Where the Sun Doesn't Shine” – A Clinicopathologic Analysis of Basal Cell Carcinoma of the Anal Region and Its Distinction from Basaloid Squamous Cell Carcinoma

Deepa T Patil, John R Goldblum, Steven D Billings. Cleveland Clinic, Cleveland, OH

Background: Basal cell carcinoma (BCC) of the anal region is rare and morphologically difficult to distinguish from basaloid squamous cell carcinoma (BSCC), particularly on biopsies. This distinction has therapeutic and prognostic implications. We reviewed morphologic features and determined the utility of Ber-EP4, bcl-2, p63, CK5/6, p16, and SOX-2 as diagnostic tools.
Design: A total of 9 BCCs and 15 BSCCs from the anal region between Jan 1993 – Jul 2011 were reviewed and analyzed for the following features: location, connection with surface epithelium, squamous differentiation, peripheral palisading, tumor retraction, mitosis/atypical mitosis, necrosis, cystic change, inflammatory response, and presence of an in-situ component. Cytoplasmic and membranous expression of Ber EP4, bcl-2, CK5/6, nuclear expression of p63, SOX-2 and nuclear and/or cytoplasmic expression of p16 were scored in a semi-quantitative manner: 1 + 1-10%, 2 + 11-50%, 3 + >50%. Statistical significance was determined using Chi2 analysis and Student t-test.
Results: All BCCs were in the perianal region while all BSCCs were in the anal canal/anorectum. Patients with BCC were slightly older (median age 71 yrs vs. 62 yrs.; p=0.09). Both had a female preponderance (F:M = 4:1 BCC vs 2:1 BSCC). BCC subtypes included nodular (4), nodular/micronodular (2), nodular/infiltrative (1), nodular/superficial (1), and superficial (1). Retraction artifact was the only statistically significant histologic feature of BCC compared with BSCC (88% vs 26%; p=0.04). Peripheral palisading of BCC approached significance (88% vs 40%; p=0.07). Atypical mitoses were more common in BSCC (71% vs 11%; p=0.05). An in-situ component was exclusively present in BSCC and noted in 6/15 cases. BCC had 2-3+ immunoreactivity for Ber-EP4 (BCC 100% vs BSCC 40%; p=0.0007) and bcl-2 expression (BCC 100% vs BSCC 33%; p=0.005). 2-3+ immunoreactivity for p16 was only seen in BSCC (BCC 0% vs. BSCC 93%; p<0.0001). All BCCs showed patchy, cytoplasmic p16 expression at the periphery of the tumor nests. SOX-2 expression was exclusive to BSCC (BCC 0% vs. BSCC 93%; p<0.0001). There was no difference in p63 and CK5/6 expression.
Conclusions: Perianal location, retraction artifact, and lack of atypical mitoses are histologic features that help distinguish BCC from BSCC. An in-situ component, when present, supports the diagnosis of BSCC. Immunostains are extremely helpful as diffuse Ber-EP4 and bcl-2 expression is a feature of BCC and BSCC is typified by diffuse p16 and SOX-2 expression.
Category: Gastrointestinal

Monday, March 19, 2012 1:00 PM

Poster Session II # 128, Monday Afternoon

 

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