p40 (ΔNp63) and Keratin 34βE12 Provide Greater Diagnostic Accuracy Than p63 in the Evaluation of Small Cell Lung Carcinoma in Small Biopsy Samples
Kelly J Butnor, James L Burchette. University of Vermont/Fletcher Allen Health Care, Burlington, VT; Duke University Medical Center, Durham, NC
Background: The use of p63 has been advocated for separating small cell lung carcinoma (SCLC) from poorly differentiated non-small cell lung carcinoma (NSCLC). However, p63 is not entirely specific in this distinction, with several studies demonstrating that a proportion of SCLCs stain for this marker. p40 (ΔNp63) is purported to be a highly specific marker for squamous cell carcinoma (SQCC). To our knowledge, the staining characteristics of SCLC for p40 (ΔNp63) have not been previous studied to any significant extent. The purpose of this study is to compare the immunohistochemical expression of p40 (ΔNp63), p63, and keratin 34βE12 in SCLC.
Design: Formalin-fixed paraffin-embedded sections from a total of 34 previously confirmed SCLCs (27 bronchoscopic biopsy samples and 7 large resection/autopsy specimens) were immunostained for p40 (ΔNp63), p63, and keratin 34βE12. Staining was defined as positive when ≥ 10% tumor cell nuclei exhibited immunoreactivity.
Results: All 34 SCLCs tested were negative for p40 (ΔNp63) and keratin 34βE12. With respect to p63, 12/27 (44.4%) bronchoscopic biopsy samples were positive, while none of the large specimens exhibited immunoreactivity. Positive and negative control tissues stained appropriately. The rate of p63 staining in bronchoscopic biopsy samples of SCLC differed significantly from that of p40 (ΔNp63) and keratin 34βE12 (P = 0.005).
Conclusions: In the first study to specifically examine p40 staining in SCLC, p40 is consistently negative in SCLC. In contrast, p63 immunoexpression is not uncommon in small biopsy samples of SCLC and may be mistakenly interpreted as supportive of squamous differentiation, resulting in misclassification of SCLC as SQCC. To provide greater diagnostic accuracy, p40 (ΔNp63) or keratin 34βE12 should be used instead of p63 in the distinction of SCLC from NSCLC in small biopsy samples.
Wednesday, March 6, 2013 1:00 PM
Poster Session VI # 292, Wednesday Afternoon