[351] The Role of p40 Immunostain in the Cytological Differential Diagnosis of Squamous Cell Carcinoma and Adenocarcinoma of the Lung

Xiangbai Chen, Yunhau Bao, Rebecca Wong, Katerina Politi, Lizhuo Jiao, Scott Gettinger, Robert Homer, Dvaid Chhieng, Guoping Cai. Yale School of Medicine, New Haven, CT

Background: Subtyping of non-small cell lung cancers (NSCLCs) has profound therapeutic implications. A panel of TTF-1/p63 immunostains is the current recommendation for differentiation of adenocarcinoma (ADC) from squamous cell carcinoma (SCC) in small biopsies or cytological specimens. However, p63 positivity, though seen in virtually all SCC cases, can be seen in as high as 30% ADCs. Furthermore, only up to 70% of ADC cases show positive TTF-1. Recently, p40 has been shown a promising marker in identifying SCC with high sensitivity and specificity on surgically resected tumors. In this study, we evaluated p40 immunoreactivity in the fine needle aspiration (FNA) specimens of lung ADCs and SCCs.
Design: The cytopathology archive was searched for the cases with FNA diagnosis of lung cancers at our institution between January 2008 to July 2012. Only the cases with the diagnosis of either ADC or SCC of the lung on surgical follow-up were included in the study. The p40 immunostain was performed on the cell-block section of FNA specimens. Nuclear staining was semi-quantatively evaluated as 0 (none), 1+ (1-25%), 2+ (25-50%), 3+ (50-75%), and 4+ (75-100%).
Results: A total of 63 cases were identified from 32 male and 31 female patients with ages ranging from 33 to 86 years. The specimens included 26 lung and mediastinal lymph node FNAs with final diagnosis of ADC on surgical follow-up in 34 cases and SCC in 29 cases. Positive p40 immunoreactivity was seen in 26 of 29 cases (90%). Only one of thirty-four ADCs (3%) was positive for p40. Interestingly, two of three SCCs with a negative p40 result were well differentiated keratinizing SCC. The only positive ADC case only had a focal positive p40 stain. The calculated sensitivity and specificity of p40 immunostain for differentiation of SCCs from ADCs were 90% and 97%, respectively.

Table 1. p40 Expression in the Cytological Specimens of Squamous Cell Carcinoma and Adenocarcinoma of the Lung
Surgical DiagnosisCase #p40 Immunoreactivity
Squamous Cell Carcinoma29335612

Conclusions: Our data demonstrate that p40 has high sensitivity and specificity for identifying lung SCCs on the FNA cell-block materials, which might be superior to p63 immunostain in the subtyping of NSCLCs.
Category: Cytopathology

Monday, March 4, 2013 1:00 PM

Poster Session II # 102, Monday Afternoon


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