Importance of the Transitional Zone between the Cervical Stroma and the Parametrium in the Treatment of Cervical Carcinoma

Objectives: Parametrial invasion is an important risk factor in cervical carcinoma. Because the vessels of the parametrium start in the zone between the cervical compact stromal layer and the parametrium, which we have defined as the parametrial initial zone (PIZ) or transitional zone, the invasion of a carcinoma into this part of the cervix is also important. Our objectives in this study were find a characteristic index of the transitional zone and to clarify the relationship between a transitional-zone invasion and the prognosis in a case. Methods: Thirty-three cases of carcinoma in situ were available to use for the morphological examination of the cervix. The cervix was divided into 8–12 sections. In each section, the outer diameters of the short axis of the arteries were measured with a light microscope and a micrometer. Using the arterial diameter as the characteristic index of the transitional zone, we performed epidemiological studies on 312 patients with clinical Stage Ib-III squamous-cell carcinoma of uterine cervix. Results: The arteries with an axis exceeding 300 μm were concentrated in the transitional zone at a rate of 94.6%. Therefore, arteries of this size are used as the characteristic index of the transitional zone. Patients with invasion to transitional zone only had lymph node metastasis at the rate of 28.1%, compared with 0% for patients who had no permeation to the zone (p < 0.001). The 5-year survival rate of patients with invasion to the transitional zone only was 87.3%, which is significantly lower than those without invasion (99.2%) (p < 0.01). Conclusions: Measuring the short axis (300 μm ≤) of the artery is the best method by which to pinpoint the transitional zone. The invasion of a carcinoma into the transitional zone in the cervix should be treated as a parametrial involvement.