Features of Malignant Tumours

Cells in malignant tumours:
-are poorly differentiated (anaplasia) and do not resemble the cell of origin either physically when viewed under the microscope or genetically.
-are poorly circumscribed.
-have higher nuclear to cytoplasmic ratio.
-exhibit nuclear pleomorphism, ie enlarged, irregular and variable nucleus which shows up under the microscope as being stained darker than the normal cells.
-darker stains due to excessive chromatin in nucleus.
-macroscopically, one would notice that the cells have an invasive edge and tumour would tend to ulcerate if it's on a surface.
-diagnosis of malignant neoplasm would be made on presence of invasion and metastasis is pathognomic of malignancy.

Spread of malignant tumours:
-direct spread
-local invasion
-permeation or infiltration of lymphatics
-perineural invasion
-vessel invasion