Abstract
The histologic grading of mode of invasion in squamous cell carcinoma of the head and neck was first proposed by Jakobsson, et al in 1973. Grade (Gr.) 4 of mode of invasion, i,e., diffuse invasion or diffuse growth, was subclassified by us into Grs.4C (cord-like type) and 4D (diffuse, widespread) for oral squamous cell carcinoma (OSCC), in 1983. Since then, clinicopathological, immunohistochemical and experimental studies for the mode of invasion have been performed to the present. The Gr.4D specific characteristics comparing with Gr.4C were observed in 1) the poorest prognosis of patients in clinical course, 2) disapearance of cell adhesion molecule corresponding with single cell invasion, 3) strong desmoplasia like as scirrhous gastric cancer in histopathology, 4) greater motility as a single cell in vitro, 5) an original strong invasion into even if "non-fibroblast" collagen gel in in vitro invasion model, 6) no up-grading from Grs.4C to 4D in experimentally induced tongue cancer, 7) no cancer invasion orthotopically transplanted into nude or SCID mouse in in vivo invasion model, in contrast to an original invasion in Grs.3 and 4C. It was concluded from these results that Gr.4D is an independent type from any other grades, and consequently, this subclassification in the mode of invasion was proven justifiable. Finally, clinical feature and treatment strategy in Gr.4D cases are discussed.
