Double staining of elastic fibre and immunohistochemistry is helpful to differentiate pleural invasion of lung cancer.

Visceral pleural invasion (VPI) is one of the critical determining factors for pathological stage of lung cancer. The pleural invasion (PL) status can be divided into four categories: PL0, PL1, PL2 and PL3, depending on the spatial relationship between the tumour tissue and outer elastic layer of pleura, visceral pleura surface and parietal pleura, respectively. Elastic stains are recommended if it is difficult to distinguish PL status by H&E staining. As reported, 19 of 100 lung cancer specimens were redefined as PL1 which were formerly deemed as PL0 by HE stain only,1 changing the stage from T1 (stage IA) to T2 (stage IB), which is essential for chemotherapy after surgery.2 Nonetheless, even assisted by elastic stains, VPI assessment is still difficult in some scenarios marked by multiple layers of elastic fibres, inflammatory infiltrates, fibrotic proliferation or carbon deposition which makes the location of scattered tumour cells barely discernible. To solve this technical problem, we developed a double staining method to show the spatial relationship between tumour cells and elastic fibres. Specifically speaking, the elastic fibres and tumour cells are stained and displayed by …