The Utility of SOX-2 as a Marker of Squamous Differentiation in Fine Needle Aspiration Biopsy Material of the Lung.
Shelley A Caltharp, Momin T Siddiqui, Cynthia Cohen, Krisztina Hanley, Gabriel L Sica. Emory University, Atlanta, GA
Background: Lung cancer is responsible for the most cancer related deaths worldwide. Introduction of new chemotherapeutic agents that are more effective in specific histologic subtypes of non small cell carcinomas has made distinguishing squamous from non squamous histologies in small biopsy specimens more important than ever in guiding clinical decision making. SOX2 is an embryonic transcription factor shown to be preferentially expressed in squamous cell carcinomas of the lung. We investigated the utility of SOX2 expression in distinguishing lung squamous cell carcinomas (SCC) from lung adenocarcinomas (ADC) in fine needle aspiration (FNA) cell blocks.
Design: Immunohistochemistry (IHC) was performed on sections from formalin fixed, paraffin embedded FNA cell blocks of 38 lung ADCs and 24 lung SCCs. SOX2 staining was evaluated for nuclear expression and graded from a scale of 1+ to 3+ and percentage positive cells. Tumors were graded as positive for SOX2 when greater than 10% of the cells showed nuclear staining. Embryonal carcinoma of the testis was used as a positive control.
Results: SOX2 IHC showed strong and diffuse nuclear expression in 67% (16/24) SCCs. The staining intensity for all SCC ranged from 2+ to 3+ with the majority showing 3+ staining. In contrast, a smaller fraction (24%, 9/38) of ADCs stained for SOX2, often with a weaker (1-2+) intensity and less number of tumor cells staining. The sensitivity of SOX2 for SCCs was 67% with a specificity of 76%, and a positive predictive value of 64%.
Conclusions: SOX2 expression is a specific marker for lung SCCs, especially when there is strong and diffuse staining. IHC for SOX2 is a valuable adjunctive marker in the diagnosis of SCCs. Due to its relatively high sensitivity and specificity, inclusion of SOX2 expression into the immunohistochemical panel of stains to distinguish lung SCC from lung ADC should be considered.
Tuesday, March 1, 2011 9:30 AM
Poster Session III # 77, Tuesday Morning