[Histological study on the early-invasive modes of oral squamous cell carcinoma].

The main purpose of this study was to Jarify the early invasive modes of carcinoma of oral mucosa. For the histological observation, the specimens were surgically removed and sectioned stepwise and serially. The results were as follows. 1. There were two types of early invasion according to the degree of invasion; primary invasion and secondary invasion. The primary invasion was observed as microinvasion from the basal layer, and the secondary invasion was observed near the muscle layer or periosteum. Before the early invasion, there were severe epithelial dysplasia which appeared to be pre-invasive. 2. The primary invasion was observed as budding, drop, and diffuse infiltration of atypical cells from the dysplastic epithelium or carcinoma-in-situ. The secondary invasion was noticed as drop and diffuse infiltration, which were morphologically similar to the invasive patterns of developmental carcinoma. 3. Downward growth of the dysplastic epithelium which was characterized by the structural atypia was observed. This type of downward proliferation of epithelium was considered to be early invasion. 4. Unclearness of the basement membrane, round cell infiltration, proliferation of the blood vessels, and loose connective tissue were seen around the early invasion. 5. Two types of malignant processes of dysplastic epitheliu; One was the process of "dysplasia--carcinoma in situ--early invasive carcinoma", the other showed a direct invasion from the dysplastic epithelium. 6. Round cell infiltration and proliferation of the blood vessels were seen near the pre-invasive epithelium or early invasion.