Single carcinoma cells at the deepest invasive portion correlate with metastatic potential of advanced colorectal carcinoma

The clinical significance of detecting single carcinoma cells (SC) at the deepest invasive portion of a tumor in terms of metastatic potential and prognosis was examined in 57 patients with surgically resected advanced colorectal carcinoma. SC were detected using an immunohistochemical stain for cytokeratin in these sections. The deepest invasive portions of tumors were subclassified by histology into three grades as follows: well-differentiated (W), moderately-well differentiated (Mw; a type that more closely resembles the W tumor), and moderately-poorly differentiated (Mp; more closely resembling poorly differentiated tumor). SC detection was defined positive if more than three single cancer cells with clear cytoplasmic expression of cytokeratin was seen distinct from carcinoma glands and tumor sheets in mid-power (x100) field. SC were detected in 51 (89%) of the 57 carcinomas. There were 5 W or Mw (W/Mw) tumors without SC, 34 W/Mw tumors with SC, 1 Mp tumor without SC, and 17 Mp tumors with SC. W/Mw tumors with SC had a significantly higher (p<0.01) incidence of lymph node metastasis than W/Mw tumors without SC. There was no lesion with lymph node or liver metastasis of W/Mw tumors without SC. SC detection, when combined with histologic subclassification at the deepest invasive portion of a tumor, correlated with prognosis. These results indicate that a combination of the tumor histologic subclassification and SC detection at the deepest invasive portion is a useful predictor of metastatic potential and prognosis in advanced colorectal carcinoma.