Peritoneal elastic laminal invasion of colorectal cancer: the diagnostic utility and clinicopathologic relationship.

To determine whether the peritoneal elastic lamina can be a useful pathologic hallmark to classify the level of tumor spreading in colorectal cancer, we performed elastica staining in 564 pT3 and pT4a colorectal cancer cases. Associations between peritoneal elastic laminal invasion of the tumor and clinicopathologic features were evaluated. Next, morphology of tumor was compared between cases with and those without peritoneal elastic laminal invasion to estimate the morphologic alteration that occurs when tumor invades beyond the peritoneal elastic lamina. Morphometric analysis of tumor area beyond the peritoneal elastic lamina was performed and compared with other tumor area to elucidate morphologic characteristics of the tumor area beyond the peritoneal elastic lamina. Clinicopathologic analysis revealed that peritoneal elastic laminal invasion was associated with higher tumor stage, palliative resection, deeper tumor invasion, deeper ulceration, over 5 mm of muscular layer elevation and peritoneal surface retraction with fibro-inflammation, higher budding grade, and high grade of lymphovascular invasion (P<0.01). Peritoneal elastic laminal invasion was associated with recurrence and prognosis in colon cancer and was an independent risk factor for the recurrence of stage II colon cancer. Furthermore, morphometric analysis revealed that tumor area in subserosal invasive front beyond peritoneal elastic lamina exhibited significantly more prominent fibrosis and tumor budding than other tumor area (P<0.01). Peritoneal elastic lamina was useful hallmark to determine the level of tumor invasion, and was powerful indicator to predict prognosis in colon cancer. Tumor area beyond the elastic lamina is characterized by extensive tumor budding and fibrosis.