A 64 year old male with a long history of tobacco use and chronic obstructive pulmonary disease was referred to the hospital from Guam for the treatment of a right upper lobe lung mass. A right upper lobectomy was done.

Pleura

While visceral pleural invasion (VPI) by non-small cell lung cancer has been recognized as an important adverse prognostic factor, the American Joint Commission of Cancer (AJCC) staging system coyly fails to identify the specific morphologic features that define invasion of the visceral pleura. A recent study (reference 1) and review article (reference 2) provide good evidence that transgression of the subpleural elastic layer (SEL) is the critical event responsible for the poorer prognosis associated with invasion of the visceral pleura.

The Japanese investigators 1 examined the degree of tumor penetration of the subpleural elastic layer and correlated the results with the clinical outcome over the next five years. The prognosis for patients whose tumor transgressed the SEL was statistically identical to those with tumor on the pleural surface, and was significantly worse than those patients whose tumors had not penetrated the SEL. The Japanese investigators affirmed pT 2 status for a tumor less than 3 cm in diameter with visceral pleural invasion, and recommended pT 3 status for a tumor greater than 3 cm in diameter with VPI.

As this case demonstrates (see green arrows in image 6), the subpleural elastic layer may not necessarily parallel the pleural surface, and may be significantly retracted over a peripheral scar carcinoma. In images 7 and 8 tumor cells clearly infiltrate through the retracted SLE. Thus, elastic stains may be of considerable value in establishing the presence of visceral pleural invasion, even when tumor cells do not appear particularly close to the pleural surface by routine H&E stains.

Image 6: Elastic Stain
green arrows = subpleural elastic layer

Image 7: Elastic Stain
green arrows = subpleural elastic layer

Image 8: Elastic Stain
green arrows = subpleural elastic layer

 References

1. Shimizu K, et al. Visceral pleura invasion classification in non-small cell lung cancer: A proposal on the basis of outcome assessment. J Thorac Cardiovasc Surg. 2004;127:1574-1578.

2. Butnor KJ, Cooper K. Visceral pleural invasion in lung cancer. Adv Anat Pathol. 2005; 12:1-6.

Comments:

Beautiful case with an excellent discussion! It is a perfect illustration of how routine surgical pathology cases can still teach us so much. Thanks!