I. BASIC PRINCIPLES
A. Neoplasia is new I issue growth that is unregulated, irreversible, and monoclonal;
these features distinguish it from hyperplasia and repair.
B. Monoclonal means that the neoplastic cells are derived from a single mother cell.
C. Qonality can be determined by glucose-6-phosphate dehydrogenase (G6PD)
enzyme iso forms.
1. Multiple isoforms (e.g., G6PDA, G6PD.,, and G6PD( ) exist; only one isoform is
inherited from each parent.
2. In females, one isoform is randomly inactivated in each cell by lyonization
(G6PD is present on the X chromosome).
3. Normal ratio of active isoforms in cells of any tissue is 1:1 (e.g., 50% of cells have
G6PDa , and 50% ofcells have G6PDG).
4. 1:1 ratio is maintained in hyperplasia, which is polyclonal (cells are derived from
5. Only one isoform is present in neoplasia, which is monoclonal.
6. Clonality can also be determined by androgen receptor isoforms, which are also
present on the X chromosome.
D. Clonality of B lymphocytes is determined by immunoglobulin (Ig) light chain
1. fg is comprised of heavy and light chains.
2. Each B cell expresses light chain that is either kappa or lambda.
3. Normal kappa to lambda light chain ratio is 3:1.
4. Thisjatio is maintained in hyperplasia, which is polyclonal.
5. Ratio increases to > 6:1 or is inverted (e.g., kappa to lambda ratio = 1:3) in
lymphoma, which is monoclonal,
E. Neoplastic tumors arc benign or malignant.
1. Benign tumors remain localized and do not metastasize.
2. Malignant tumors (cancer) invade locally and have the potential to metastasize.
F. Tumor nomenclature is based on lineage of differentiation (type of tissue produced)
and whether the tumor is benign or malignant