How do you tell when cells are cancerous?

Answer 1

Cancerous cells exhibit uncontrolled and inappropriate mitosis. Cancerous cells will often exhibit changed morphology and gene expression profiles, often assuming the shape and gene expression of more immature or more stem-like cells (a process termed de-differentiation). Cancerous cells often exhibit unusual karyotypes. Clinically, the precise identification of a cancerous cell can be difficult and will vary tissue to tissue. Another consideration is that for at least some cancers it is theorized that only a small proportion of cells within a tumor are actively cancerous. These cells are referred to as cancer stem cells. It is theorized that in some cases only a comparatively few cells are genuinely tumor-forming (i.e. uncontrollably dividing) and generating large growths of non-tumor forming cells of the visible tumor. Identifiying these actively tumor-forming cells remains a challenge in oncology.

Answer 2

Cancer cells often exhibit abnormal growth patterns, rapid division, and an inability to respond to normal signals that regulate cell growth. They may also have unusual shapes, sizes, and structures when compared to normal cells. Additionally, cancer cells can spread to other parts of the body, unlike normal cells which remain localized. Ultimately, a definitive diagnosis of cancer requires a biopsy and examination by a pathologist.