Pathology

• Clinical classification – covers the clinical presentation and outcome. EX: benign and malignant tumors
• Histological classification – The microscopic examination of the tumor to determine the cell type, degree of differentiation and some aspects of invasion

• Looking at a tumor grossly (without a microscope) or by imaging with a CT or MRI can determine a lot about the tumor.
• Benign tumors usually have sharp borders and appear well contained.
• Malignant tumors often show a diffuse pattern of spread with involvement of adjacent tissues.

• This is the area where anatomical certified pathologists make their living. There are common features of malignancy such as variation between cells as to size and shape (pleomorphism), increased ratio of nucleus to cytoplasm and a pattern of growth showing invasion.
• Some tumor have unique features and unique surface markers that allow their identification. It is important to determine the source and type of tumor as this often determines appropriate therapy.

• Most benign tumors have a normal complement of chromosomes.
• Malignant tumors often have an abnormal number (aneuploid)

Some tumors if well differentiated carry out some functions of that cell type. Other poorly differentiated tumors spend all their energy on growth alone

• The phenomena by which tumor cells live the primary site and invade other tissues.
• These cells can travel by blood vessels (hematogenous) and by the lymphatics.
• The definition of malignancy may really be the ability of these tumor cells to escape immunological control and move to other areas of the body and establish a new home.
• The ability to produce angiogenic factors allows these tumors to provide nutrition in their new environment.

malignant proliferation of plasma cells

benign proliferation of plasma cells

• that tumor derived from connective tissue cells like fat, fibroblasts, bone, blood vessels, and muscle when benign have the suffix "oma". Examples are lipoma, fibroma, osteoma etc.
• When the cells are malignant the suffix "sarcoma" is added. Examples are Liposarcoma, fibrosarcoma, and osterosarcoma.

• The benign tumors from epithelial cells (lining cells and organ cells) have the suffix "oma" or are often called "adenoma". Examples are Thyroid adenoma, Gastric adenoma, or salivary gland adenoma.
• When these epithelial cells are determined to be malignant we use the work "carcinoma". Examples would be Thyroid carcinoma, Gastric carcinoma and salivary gland carcinoma

• There are different nomenclatures for some specific tumors and for tumors of the hemopoietic (white and red blood cells) .
• An example is a benign proliferation of plasma cells is called a plasmacytoma
• and a malignant proliferation of plasma cells is called Multiple Myeloma.

Tumors derived from embryonic cells may have suffix "blastoma" or teratomas

• Some tumors cannot be appropriately named as to malignant and benign until their biological behavior is determined.
• Example tumors of some endocrine organs.

Staging is very clinically important based on tumor size, presence of lymph node involvement and distant metastases

• Grading of tumors may be useful in determining the aggressiveness of tumor.
• Grade I are well differentiated, that is they look a lot like parent cells,
• Grade II are moderately well differentiated, that is they still look somewhat like cells or origin and
• Grade III, poorly differentiated, cannot easily determine the cells of origin.

Causes of human cancer is unknown

• A. Causes can be divided into exogenous (outside) and endogenous (inside)
• 1. Exogenous include chemicals, physical agents and viruses
• 2. Endogenous causes involve the genome of the cells and are heritable.