[1290] Identification of Sox2 as a Marker for Ameloblastic Carcinoma

Yu Lei, Jumana M Jaradat, Adepitan A Owosho, Kehinde E Adebiyi, Elizabeth A Bilodeau. University of Pittsburgh School of Dental Medicine, Pittsburgh, PA; Obafemi Awolowo University, Ile-Ife, Nigeria

Background: Recent interrogations of the cancer genomes of multiple solid tumors reveal prominent amplifications of the gene encoding Sox2. In fact, Sox2 is pivotal in maintaining the renewal potential of stem cells and inhibiting their differentiation. Ameloblastic carcinoma is a malignancy of odontogenic origin with a dismal prognosis. Separation of this entity from its benign counterparts may be challenging in specimens where atypical features are present. In this study, we aim to assess the diagnostic value of Sox2 in differentiating ameloblastic carcinoma from ameloblastoma.
Design: 4 ameloblastomas (AB), 3 atypical ameloblastomas (AA), 3 ameloblastic carcinomas (AC) (the tissue block of 1 consult AC was unavailable for additional staining), and 3 dentigerous cysts (DC) were included. Immunohistochemical studies were performed on tissue blocks with antibodies against Sox2, CD56, CD138, SMA, Calretinin, and β-catenin. Immunostains were interpreted by 3 pathologists, and scores were recorded based on the areas of stains (1-4 depicting 0-25%, 26-50%, 51-75%, and 76-100%, respectively) and intensity of stains (0-3 depicting negative, minimal, intermediate, and strong staining, respectively) in the cells of interest. Kruskal–Wallis one-way ANOVA was employed to compare the ameloblastic groups.
Results: Sox2 showed strong diffuse nuclear positivity in the 2 stained AC compared to few to none scattered positive cells in either AB or AA (P=0.078). Sox2 highlighted the basal proliferative zone of epithelium in DC. None of the previously reported ameloblastic markers could separate AC from its benign counterparts. Both CD56 and CD138 were variably positive in all ameloblastic and DC epithelium except 1 AB specimen marking as CD56-, CD138+. Scattered positive cells with β-catenin nuclear staining were present in 2 AB specimens. Although previously suggested as a sensitive ameloblastic marker, Calretinin was only positive in 5 of 10 cases.
Conclusions: Sox2 is a novel marker that readily differentiates AC from AB with a distinct diffuse nuclear staining in the former. The P value was not significant due to the limited sample size. However, we have initiated a broader collaboration to further characterize Sox2 in AC. Previous studies suggest diffuse Sox2 stain correlates with a poor prognosis and a more aggressive clinical course in multiple malignancies including oral squamous cell carcinoma. Strong Sox2 expression in tumor cells may recapitulate one of the hallmarks of cancer, loss of differentiation coupled with uncontrolled renewal.
Category: Head & Neck

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 191, Monday Morning


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