Myofibroblast distribution is associated with invasive growth types of colorectal cancer

Both the invasive growth types of colorectal cancer (CRC) and the number of myofibroblasts have been associated with histopathological factors such as lymph node and liver metastasis, and local recurrence. However, there are few studies, that have assessed the association between invasive growth type and myofibroblast distribution in CRC. We aimed to evaluate the relationship between the clinicopathological factors of CRC and two invasive growth types, the expanding and infiltrating types. We categorized 150 cases of pT3 CRC into the expanding and infiltrating types and measured the myofibroblast density of three histological layers: the submucosa (SM), the muscularis propria (MP) and the subserosa (SS). We compared these two invasive growth types and analyzed the relationship between clinicopathological factors and myofibroblast density. Myofibroblast density was significantly higher in the infiltrating type than that in the expanding type (P<0.05). In the lymph node metastasis-positive group of the infiltrating type, myofibroblast density in MP was significantly higher than that in the lymph node metastasis-negative group (P<0.001). In the infiltrating type, the group with the higher level of lymphatic invasion had a significantly higher density of myofibroblasts in the MP than the group with the lower level of lymphatic invasion (P<0.01). These results suggest that myofibroblasts participate more in the infiltrating type compared with the expanding type of CRC. It would appear that myofibroblasts present in the MP play an important role in the malignant potential of the infiltrating type compared to the expanding type.