[1314] Immunohistochemical Expression of p40 in Sarcomatoid Squamous Cell Carcinoma of the Head and Neck

Kamille A West, Darren J Buonocore, Violette Ghali, Beverly Wang. Beth Israel Medical Center, New York, NY

Background: Sarcomatoid or spindle cell squamous carcinoma (SCSC) of the head and neck is an uncommon histologic subtype that may present considerable diagnostic difficulty on routine histology. Conventional squamous cell carcinomas are known to express p63, however this marker is not entirely specific for squamous differentiation. p40 has been recently shown to be as sensitive and more specific than p63 for squamous cell carcinoma in the diagnosis of non-small cell lung cancer. To the best of our knowledge, there do not appear to be any studies in the English medical literature examining the utility of p40 staining in SCSC. We sought to investigate the diagnostic utility of p40 immuohistochemistry in this aggressive variant.
Design: We searched our archives for all cases of SCSC of the head and neck region diagnosed from January 2008 to July 2012. Hematoxylin and eosin stained slides were reviewed. Five (5) head and neck sarcomas were selected as controls, comprising two high-grade sarcomas, a soft tissue malignant myoepithelioma, a monophasic synovial sarcoma and a chondroblastic osteosarcoma. p63 and p40 immunohistochemistry was performed on all cases and controls.
Results: Twenty-two (22) cases of SCSC were identified. In these cases, p63 was expressed in more cases than p40 (18/22 vs 13/22). Thirteen (13) cases showed strong and diffuse positivity for p63, 5 showed focal or rare cells positive and 4 cases were negative. Interestingly, none of the cases showed stronger staining for p40 than p63. The results of immunochemical staining are summarized in Table 1.

Among the sarcoma controls, only the monophasic synovial sarcoma showed focal positivity for p63; all other sarcomas were negative. Of note, the chondroblastic osteosarcoma displayed nuclear positivity for p40; however, this entity should be easily distinguished from sarcomatoid squamous cell carcinoma on morphologic grounds. All other sarcomas were negative for p40.
Conclusions: p63 and p40 are both expressed in SCSC. p40 is relatively underexpressed, and is less sensitive than p63 in these tumors. Due to the small size of available cases, specificity could not be accurately evaluated. Based on our findings there appears to be no advantage to using p40 over p63 in the diagnosis of SCSC.
Category: Head & Neck

Wednesday, March 6, 2013 9:30 AM

Poster Session V # 194, Wednesday Morning

 

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