Neoplasms

Neoplasms are classified according to whether they are benign or malignant as well as the tissue and cell type from which they arise. The term "cancer" is used synonymously with the term "malignant neoplasm."

Some major differences between benign and malignant neoplasms are as follows:

• The cells in a benign neoplasm remain clustered together in a single mass whereas the cells in a malignant tumor have acquired the ability to invade surrounding tissue. Thus in the case of a malignant neoplasms arising from epithelial cells, the cells have not yet penetrated the basement membrane (sometimes called a carcinoma in situ)

• Metastasis is the ability of cells to break loose and enter the bloodstream or lymphatic vessels and form secondary tumors called "metastases" at other sites in the body is a possibility in malignant neoplasms whereas it does not occur in the benign neoplasm.

• Benign neoplasms have a normal nucleus to cytoplasm ratio whereas malignant neoplasms have a high nucleus-cytoplasmic ratio (the nucleus has a relatively large nucleus with scanty cytoplasm).

• benign neoplasms have a normal chromosomal number (ploidy) whereas malignant neoplasms have increased ploidy

• The cells of a benign neoplasm resemble cells of origin whereas the cells of a malignant neoplasm exhibit anaplasia which is the loss of structural differentiation.

• Whereas benign neoplasms can exhibit dysplasi which is the disorderly, but non-neoplastic proliferation, malignant neoplasms exhibit metaplasia which is the abnormal transformation of a fully differentiated adult tissue of one kind into a differentiated tissue of another kind. For example, a simple columnar epithelium of the colon will develop thousands of polyps which are macroscopic projections resembling a tiny cauliflower above the mucosal surface. Other abnormal transformations associated with some malignant neoplasms might include a papilloma which are micro or macroscopic apytical finger like projections and ademonas which are neoplasms that produce gland patterns, and cystademonas which are hollow cystic masses.

• benign neoplasms are characterized by slow growth whereas such growth is rapid in malignant neoplasms.

• angiogenesis is common in benign neoplasms whereas it is extensive in malignant neoplasia.

Neoplasms which are benign have the ending "oma." Neoplasms which are malignant and arise from epithelial cells are termed "carcinomas" whereas those arising from connective tissue or muscle cells are termed "sarcomas". For example, a benign neoplasm originating in the surface epithelium would be termed a "papilloma" whereas it would be termed a "carcinoma" if malignant. Similarly, a benign neoplasm originating in the fibrous tissue would be termed "fibroma" whereas it would be termed "fibrosarcoma" if malignant. A benign neoplasm originating in the bone would be called an "osteoma" whereas it would be called an "osteosarcoma" if malignant.

Neoplasms can be further characterized based on the grade or differentiation of the neoplasms as well as the stage which is the size and anatomical extent of the neoplasm. Neoplasms which are differentiated have lower grades (i.e., grade I for well differentiated) whereas those which are poorly differentiated have higher grades up to grade IV. Similarly, neoplasms which are localized have lower stages (stage A) whereas those which have started to spread have higher stages (i.e., stage C for distant spread).