Utility of five commonly used immunohistochemical markers TTF-1, Napsin A, CK7, CK5/6 and P63 in primary and metastatic adenocarcinoma and squamous cell carcinoma of the lung: a retrospective study of 246 fine needle aspiration cases

Abstract

Background: Fine needle aspiration (FNA) biopsy plays a critical role in the diagnosis and staging of lung primary and metastatic lung carcinoma. Accurate subclassification of adenocarcinoma (ADC) and/or squamous cell carcinoma (SqCC) is crucial for the targeted therapy. However, the distinction between ADC and SqCC may be difficult in small FNA specimens. Here, we have retrospectively evaluated the utility of TTF-1, Napsin A, CK7, P63 and CK5/6 immunohistochemical (IHC) markers in the distinguishing and subclassification of ADC and SqCC.

Methods: A total of 246 FNA cases were identified by a computer search over a two-year period, including 102 primary NSCLC and 144 primary NSCLC which had metastasized to other sites. The immunostaining patterns of TTF-1, Napsin A, CK7, P63 and CK5/6 were correlated with the histological diagnosis of the tumor.

Results: In 72 primary ADCs, TTF-1, Napsin A and CK7 showed a sensitivity and specificity of 84.5%/96.4%, 92.0%/100%, and 93.8%/50.0%. In 30 primary SqCCs, CK5/6 and P63 showed a sensitivity and specificity of 100%/77.8% and 91.7%/78.3%. In 131 metastatic ADCs, Napsin A showed the highest specificity (100%), versus TTF-1 (87.5%) and CK7 (25%) but decreased sensitivity (67.8% versus 86.9% and 100%); whereas in 13 metastatic SqCCs, CK5/6 and P63 showed a sensitivity/specificity of 100%/84.6% and 100%/68.4%. Bootstrap analysis showed that the combination of TTF-1/CK7, TTF-1/Napsin A and TTF-1/CK7/Napsin A had a sensitivity/specificity of 0.960/0.732, 0.858/0.934, 0.972/0.733 for primary lung ADCs and 0.992/0.642, 0.878/0.881, 0.993/0.618 for metastatic lung ADCs.

Conclusions: Our study demonstrated that IHC markers had variable sensitivity and specificity in the subclassification of primary and metastatic ADC and SqCC. Based on morphological findings, an algorithm with the combination use of markers aided in the subclassification of NSCLCs in difficult cases.

Keywords: CK7; Cytopathology; Fine needle aspiration (FNA) cytology; Immunohistochemical (IHC) marker; Napsin A; Non-small cell lung carcinoma (NSCLC); P63 and CK5/6; TTF-1.

Figure 1

Immunostaining pattern of CK5/6 and P63 in squamous cell carcinomas. A, histomorphology of SqCC on H&E slide; B, immunostain of CK5/6 in tumor cells, C, immunostain of P63 in tumor cells, and D, stain of TTF-1 in tumor cells and entrapped normal lung bronchial epithelium. Tumor cells of SqCC are positive for CK5/6 and P63, but negative for TTF1.

Figure 2

Immunostaining pattern of TTF-1, Napsin A and CK7 in adenocarcinomas. A, histomorphology of ADC on H&E slide; B, immunostain of TTF-1 in tumor cells, C, immunostain of Napsin A in tumor cells, D, stain of CK7 in tumor cells, E, stain of P63 in tumor cells, and F, stain of CK5/6 in tumor cells. Tumor cells of ADC are positive for TTF-1, Napsin A and CK7, but negative for P63 and CK5/6.

Figure 3

The sensitivity and specificity of IHC markers, as individual or in combination, in primary lung adenocarcinomas by the bootstrap resampling analysis.

Figure 4

The sensitivity and specificity of IHC markers, as individual or in combination, in metastatic lung adenocarcinomas by the bootstrap resampling analysis.

Figure 5

The sensitivity and specificity of IHC markers, as individual or in combination, in primary lung squamous cell carcinomas by the bootstrap resampling analysis.

Figure 6

The sensitivity and specificity of IHC markers, as individual or in combination, in metastatic squamous cell carcinomas by the bootstrap resampling analysis.

Figure 7

Outline of an algorithmic approach in the subclassification of NSCLC using FNA cases. In the algorithm, the evaluation of cytological morphology in the conjunction of immunostaining patterns is necessary for the final diagnosis of the tumor and/or further decision-making steps.