Desmoplastic reaction (DR), which is characterized by stromal fibrosis of invasive carcinomas, is thought to start increasing when carcinoma cells have invaded beyond the muscularis mucosae [8
]. On the other hand, Martin et al.
reported that the dense fibroblastic reaction is capable of restraining the progression of tumor cells and plays a role in tumor regression [10
]. The differences in these articles may have arisen due to the complex crosstalk mechanisms between the carcinoma and stroma.
In the multicenter collaborative studies led by the Japanese Society for Cancer of the Colon and Rectum
], we previously demonstrated that the biopsy specimens from Group B were frequently evaluated as DR-positive lesions. These pathological examinations were performed on sections stained with H & E. Thus, these studies revealed that it is possible to predict SM depth by diagnosis of pretreatment biopsy specimens, especially in non-pedunculated, but not in pedunculated CRCs.
It is generally known that growth of myofibroblasts is affected not only by tumor progression but also by inflammatory or mechanical stimulation, and indeed, pedunculated colorectal tumors (such as pedunculated M CRC, Juvenile type polyp, Peutz-Jeghers type polyp and mucosal prolapse syndrome) tend to have abundant myofibroblasts around the muscularis mucosae, regardless of histological malignancy. In our former studies, we found that it was difficult to diagnose DR in some biopsy specimens from non-pedunculated CRCs that were stained with H&E. To resolve this problem, the present study was carried out to detect the presence of DR using biopsy specimens, immunostained for αSMA and desmin, and to determine whether or not the discrimination accuracy between Groups A and B could be improved.
In our retrospective study, the calculated sensitivity, specificity, PPV and NPV of DR positivity to differentiate Group A from Group B were 64.8%, 65.2%, 91.9% and 23.3%, respectively [6
]. Subsequently, in our prospective study, the calculated sensitivity, specificity, PPV and NPV of DR positivity to differentiate Group A from Group B were 68.6%, 92.0%, 94.6% and 59.0%, respectively [1
]. However, in this study, the calculated sensitivity, specificity, PPV and NPV of DR positivity to differentiate Group A from Group B were 87.5%, 100%, 100% and 82.4%, respectively. Thus, the sensitivity, specificity, PPV and NPV from the current study were markedly increased compared with the previously results. In particular, it was remarkable that DR-positive lesions were all Group B CRCs.
Although DR wasn’t detected in pretreatment biopsy specimens of the three cases in Group B, DR positivity was shown in the resected specimens from all of them. The endoscopic findings of them were all sessile. The mean tumor size of the three lesions was 20.7 mm (range, 20 to 22 mm), which was 7.7 mm greater than that of all 38 lesions. In retrospect, it seemed that inappropriate biopsies were performed in these 3 cases; inappropriate biopsies were defined as those taken at the edge of the tumor, but without the presence of SM2. Consequently, if the biopsies had included SM2 of the lesions, all Group B cases would have been accurately diagnosed with DR.