JMIR Publications

ABSTRACT

Background:

What is a tumor, viz. how to define it? This seemingly naïve question has for years nagged at us as pathologists or other medical professionals who study cancer. This is because tumors are defined differently in the literature from different viewpoints, such as from the slants of evolution, morphology, clinical manifestation, etc., and whether some outgrowths such as keloids are neoplastic or not are still debatable.

Objective:

This essay aims to present our definitions of outgrowths and cell deaths, and then to propound our idea that more researches should be put on benign neoplasms.

Methods:

We summarized key pathological features of cellular outgrowths to distinguish neoplastic lesions from non-neoplastic ones and summarized descriptions of cell deaths from the literature to bolster our viewpoint on apoptosis. We also present features of, and differences between, benign and malignant neoplasms, which lead to the inference that studies on tumorigenesis should first be focused on the benign neoplasms.

Results:

Benign neoplastic cells are immortal and autonomous, and autonomy can be manifested in either cellular replication or cellular function. Malignant cells have additional attributes, including decreased differentiation, more epigenetic and genetic alterations, invasiveness, metastatic potential, therapeutic refractoriness, etc. Of these traits, however, only cellular immortality and autonomy are unique and are indispensable criteria for rating a neoplasm, whereas the others can all be discerned in certain normal cells. the apoptosis originally defined by Kerr et al. is evolutionarily developed to remove obsolete or redundant cells like hyperplastic ones, but some neoplastic cells may also die of apoptosis because they retain certain stalwart to their parental organism. Efforts of the research fraternity have hitherto been put mainly on the malignancies, which have too many tangled alterations for researchers to disentangle.

Conclusions:

Tumorigenesis should probably be studied in two steps: The first is to Identify the cellular or molecular alterations that are the proximate causes for cellular immortality and autonomy, for which benign neoplasms or cell lines may be better models because they have many fewer alterations than their malignant counterparts. The second step is to study the malignant properties using malignant neoplasms or cell lines as model systems.