Purpose: Myofibroblasts, which are specifically differentiated fibroblasts, are thought to play a central role in the desmoplastic reaction, a dynamic stromal change closely associated with cancer development. Although fundamental studies suggest that myofibroblasts may either facilitate or inhibit cancer progression, cumulative evidence supports their role in promoting tumor progression. The aim of this study was to assess the value of myofibroblasts in the cancer stroma as an indicator of disease recurrence after colorectal cancer surgery.

Experimental Design: Using computer-assisted image analysis, we quantified myofibroblasts in the cancer-associated stroma of 192 colorectal cancers using α-smooth muscle actin as a marker.

Results: The cancer-associated stroma contained various numbers of myofibroblasts (0.35-19.0%; mean, 5.55 ± 3.85%). Tumors with abundant myofibroblasts were associated with shorter disease-free survival rate (P = 0.001) for stage II and III colorectal cancer. Multivariate analysis indicated that α-smooth muscle actin was a significant prognostic factor comparable with lymph node metastasis and superior to other tumor and stromal components, including histology of the tumor invasive front, peritumoral lymphocytic infiltration, and Crohn's-like lymphoid reaction. Moreover, colorectal cancers with synchronous liver metastasis generally displayed an active desmoplastic reaction, which was retained in the metastatic lesion to a similar extent.

Conclusions: The results suggest that the abundance of myofibroblasts in cancer-associated stroma may be a useful indicator of disease recurrence after curative colorectal cancer surgery.