Abstract.Lymph nodes from patients with colorectal cancer were immunohistochemically stained for cytokeratin to investigate the relationship between the presence of occult neoplastic cells (ONCs) and recurrence/metastasis. A total of 80 patients with stage III/Dukes' C colorectal cancer were divided into 16 patients who developed recurrence/metastasis (recurrence group) and 64 patients without recurrence (nonrecurrence group). ONCs were compared between the two groups with respect to i) single cells (≥3 floating ONCs), ii) clusters of cells (1 or more floating aggregates of 2-20 ONCs) and iii) single cells + clusters. When single cells were detected, the sensitivity for recurrence was 87.5% (14/16, p=0.002), the positive predictive value (PPV) was 32.6% (14/43), the specificity was 54.7% (35/64) and the negative predictive value (NPV) was 94.6% (35/37). For clusters, the sensitivity was 87.5% (14/16, p<0.001), PPV was 41.2% (14/34), specificity was 68.8% (44/64) and NPV 95.7% (44/46). With single cells + clusters, the values were 87.5% (14/16, p<0.001), 48.3% (14/29), 76.6% (49/64) and 96.1% (49/51), respectively. These results suggest that the detection of single cells + clusters is a sensitive indicator of a high risk of recurrence/metastasis, while ONCs are useful for identifying the low-risk group of patients with stage III colorectal cancer.
IntroductionThe 5-year survival rate of Japanese patients who have stage II/ Dukes' B colorectal cancer without lymph node metastasis and receive curative resection is approximately 80% (colon, 84.5±2.8%; rectum, 79.8±4.0%), whereas the 5-year survival rate is considerably lower at approximately 60% (colon, 74.0±3.5%; rectum, 64.7±4.3%) for patients with stage III/ Dukes' C colorectal cancer and lymph node metastasis who undergo curative resection (1-4). Thus, recurrence/metastasis develops in 30-40% of stage III/Dukes' C patients after curative resection and can be fatal (2,4). According to the pathological concept of breast cancer, positive lymph node metastasis indicates systemic disease with the potential for metastasis to other organs and the presence or absence of lymph node metastasis is considered to be one of the most important clinical markers (5,6). Hematogenous metastasis to the liver or the lungs in patients with lymph node metastasis who undergo curative resection is presumed to occur when cancer cells circulating in the blood during the perioperative period, escape the immune system enter the microcirculation of the liver or the lungs, and find appropriate microenvironment for growth and proliferation (7-10). Various reports have been published about the close relationship between recurrence/metastasis of cancer and detection of occult neoplastic cells (ONCs) positive for cytokeratin immunohistochemical staining and floating in the sinuses of lymph nodes distant from the primary tumors (11-15). ONCs can be semiquantified by a relatively simple immunostaining method and represent floating tumor cells target trapped in the microcirculation of the lymph node...