p40 (ΔNp63) is more specific than p63 and cytokeratin 5 in identifying squamous cell carcinoma of bronchopulmonary origin: a review and comparative analysis.

The therapeutic options now available for pulmonary squamous cell carcinoma (SQCC) and adenocarcinoma (ADC) are very different. The increasing demand to make a diagnosis on minimal tissue, ancillary techniques such as immunohistochemistry (IHC) are need to be highly sensitive and specific. The IHC marker p40 (ΔNp63) is a truncated isoform of p63 that is a promising IHC marker for SQCC. In this study, we have compared the specificity of p40(ΔNp63) IHC with p63 and cytokeratin 5 (CK5) on fine-needle aspiration (FNA) cell blocks (CB). Thirty cases of pulmonary SQCC and 30 cases of pulmonary ADC with CB were selected. IHC for p40(ΔNp63), p63, and CK5 were performed on all paraffin-embedded CB serial sections. All cases (n = 30) of SQCC stained positive for p40(ΔNp63). All cases of bronchopulmonary ADC were negative for both p40(ΔNp63) and CK5. Six cases (20%) of bronchopulmonary ADC demonstrated nuclear staining for p63 in at least 10% of malignant cells. Our data support p40(ΔNp63) to be more sensitive and specific and possess a greater positive and negative predictive value for SQCC in comparison to p63. This study also documents that p40(ΔNp63) does not stain ADC, which p63 does in 20% of the cases. We also found that p40(ΔNp63) shows a greater sensitivity and negative predictive value when compared to CK5. In paucicellular CB the increased indices p40(ΔNp63) provides may be extremely helpful in confirming the diagnosis of SQCC, which may have significant therapeutic implications.