Characterization of pleural metastasis in non-small cell carcinomas undergoing intraoperative frozen section examination

Abstract

Background: Pleural biopsy via open surgery or video-assisted thoracoscopic surgery is consistently performed in patients with non-small cell lung carcinoma (NSCLC) for diagnostic tumor confirmation, tumor staging, and tumor tissue acquisition. We investigated the clinicopathological characteristics of pleural metastasis in NSCLC, with a specific focus on the comparison between adenocarcinoma (ADC) and squamous cell carcinoma (SqCC). This study aimed to quantify how intraoperative gross finding predicts a positive-for-malignancy (PFM) diagnosis on frozen sections and to delineate histology-specific microscopic features distinguishing ADC from SqCC in PFM cases.

Methods: A retrospective analysis was conducted on 237 pleural biopsies, which underwent intraoperative frozen examination between March 2000 and February 2015. Clinicopathologic parameters, including intraoperative visual inspection and microscopic findings, were assessed in 112 NSCLC patients (75 ADC and 37 SqCC).

Results: Among 112 NSCLC cases, the presence of pleural nodularity during the operative procedure was identified as an independent predictor for pleural metastasis [odds ratio (OR) 8.33, 95% confidence interval (CI): 3.36-20.65, P<0.001]. Microscopic examination revealed that sclerotic fibrosis was associated with pleural metastasis in ADC (OR 6.56, 95% CI: 1.71-25.26, P=0.006), whereas metastatic SqCC exhibited a higher inflammatory component than ADC (80.0% vs. 30.1%, P<0.001), albeit without significant prediction for pleural metastasis in SqCC.

Conclusions: Pleural nodularity in operative field strongly indicated pleural metastasis in NSCLC. Additionally, ADC and SqCC exhibited distinct microscopic characteristics, with sclerotic fibrosis frequently accompanying pleural metastasis in ADC.

Keywords: Non-small cell lung carcinoma (NSCLC); frozen section; metastasis; pathology; pleura.

Figure 1

Diagram of the study population. NFM, negative for malignancy; PFM, positive for malignancy.

Figure 2

Different inflammatory pattern observed in pleural metastasis of adenocarcinoma and squamous cell carcinoma [hematoxylin and eosin stain; original magnification ×100 (A) and ×200 (B)]. Metastatic adenocarcinoma of pleura has inflammation at the periphery of tumor (A). Note the distinguished tumor cells (left) and inflammatory cells (right) by dotted line. Meanwhile, inflammatory cells are more intermingled with tumor cells in metastatic squamous cell carcinoma (B).

Figure 3

Different fibrous pattern observed in pleural metastasis of adenocarcinoma and squamous cell carcinoma (hematoxylin and eosin stain; original magnification ×200). Sclerotic fibrosis (*) is frequently accompanied by pleural metastasis of adenocarcinoma (arrows), and also an independent predictor of pleural metastasis in adenocarcinoma (A). In contrast, metastatic squamous cell carcinoma (arrowheads) frequently accompanies loose fibrosis (**) (B).