The fallacy of the concept of invasion--critique in historical perspective with implications for diagnosis of early malignant neoplasms.

In recent years, attempts have been made to enhance reproducibility in reporting early cancerous lesions. For this purpose, specific diagnoses in the language of clinical medicine have been substituted by nonspecific designations that encompass benign and malignant processes, such as "squamous intraepithelial lesion" and "melanocytic intraepidermal neoplasia." The propagation of noncommittal terms for all in situ lesions has, in turn, led to a renaissance of the old concept of invasion as a prerequisite for the diagnosis of cancer. Invasion, that is, transgression of the epithelial basement membrane by at least 1 neoplastic cell, is difficult to recognize, can never be excluded, and has little, if any, prognostic significance. Nevertheless, the concept that malignancy requires invasion, deeply rooted in the history of pathology, gave legitimacy to evasive terms that serve to conceal diagnostic difficulties but do not resolve them. The pillars of this concept are based on outdated suppositions of the 19th century that have no place in modern medicine.