Cytologically, neoplasia is characterized by the presence of a homogeneous population of cells that have come from the same
tissue of origin. This is best appreciated by the presence of cells with the same cytoplasmic characteristics. If a neoplasm
is diagnosed, two important determinations must be attempted: 1) is the lesion benign or malignant, and 2) what is the tissue
Benign vs. Malignant
Benign neoplasia / hyperplasia is characterized by a uniform population of cells. There should be a uniform cytoplasmic and
nuclear size and shape, uniform nuclear to cytoplasmic ratio, and if nucleoli are present, they are of consistent size, shape,
and number among individual cells.
Malignant neoplasms will have nuclear features that are considered abnormal and indicate a cell population that is growing rapidly and uncontrollably.
The following are nuclear characteristics considered to be abnormal.
3. High or variable N:C ratio
4. Increased mitotic activity
5. Nucleoli that vary in size, shape, and number (angular, irregularly shaped nucleoli)
6. Coarse chromatin or uneven margination of chromatin at nuclear membrane
7. Nuclear molding
If many of the cells show 3 or more of the criteria of malignancy, the tumor is malignant. In the vast majority of the cases,
the cytologic criteria of malignancy are accurate predictors of the potential biological behavior of the tumor. Most tumors
with malignant features will either be locally invasive or have the potential for metastasis. However, there are some circumstances, and these are the exception to the rule, where the cytologic appearance may not accurately predict the biological behavior. A practicing cytologist must be aware
of the exceptions to the rule in order to be able to rely on cytology to provide meaningful, accurate information regarding
the prognosis of a patient.