Neoplasm PDF - A Detailed Overview

NEOPLASM HELEN OWUSU-ASANTE(MRS) INTRODUCTION  Cell growth and cell death are normally balanced so that a stable number of cells are maintained in a given tissue.  Occasionally, however, cells arise that no longer respond to the usual checks and balances for division and death.  Suc...

NEOPLASM HELEN OWUSU-ASANTE(MRS) INTRODUCTION  Cell growth and cell death are normally balanced so that a stable number of cells are maintained in a given tissue.  Occasionally, however, cells arise that no longer respond to the usual checks and balances for division and death.  Such growths are called NEOPLASM OR TUMOUR. (Used interchangeably)  Typically, there is irreversible DNA damage, resulting in autonomous growth of abnormal cells. DEFINITION  Abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the normal tissues and persists in the same excessive manner after apparent cessation of the stimuli which evoked the change.-Sir Rupert Willis, 1952  An abnormal mass could be hyperplasia (increase in number of cells), hypertrophy (increase in size of organ or tissue as a response to increased demand) or inflammation (living tissue response to injury) NOT NEOPLASMS, when stimulus is removed, process is reversed.  The study of neoplasms or tumours is ONCOLOGY  NOTE: The entire population of neoplastic cells within an individual tumor arises from a single cell that has incurred genetic change, and hence tumors are said to be CLONAL.  They result from mutations of genes that regulate Cell growth, Apoptosis and DNA repair  The stimuli for such uncontrolled proliferation are either acquired spontaneously or induced environmentally or even still unknown  Tumors can vary in size from a tiny nodule to a large mass, depending on the type, and they can appear almost anywhere on the body. However, only some types of tumours threaten health and life. CAUSES OF TUMOURS  The environmental factors include:  They result from mutations of genes ❖ Infectious agents e.g. viruses that regulate Cell growth, Apoptosis ❖ Smoking and DNA repair. ❖ Alcohol consumption. ❖ Diet.  The stimuli for such uncontrolled proliferation are either acquired ❖ Obesity. spontaneously or induced ❖ Reproductive history environmentally or even still unknown ❖ Carcinogens e.g. radiation ❖ Age  There are three main types of neoplasm/tumor:  BENIGN: These are not cancerous. They either cannot spread or grow, or they do so very slowly. If surgically removed, they do not generally return.  Benign tumors remain localized to the area in which it originated and pose little risk to health  Nevertheless, though benign tumours are incapable of dissemination, they can expand and place pressure on organs, causing signs or symptoms of disease.  In some cases benign tumours that compress vital structures can cause death—for instance, tumours that compress the brainstem, where the centres that control breathing are located.  PREMALIGNANT: In these tumors, the cells are not yet cancerous, but they have the potential to become malignant.  MALIGNANT: Malignant tumors are cancerous. The cells can grow and spread to other parts of the body.  The process of spread, accompanied by the seeding of tumour cells in distant areas, is known as metastasis.  Malignant tumors invade and destroy healthy tissues in the body’s major organ systems by gaining access to the circulatory or lymphatic systems.  It is not always clear how a tumor will act in the future. Some benign tumors can become premalignant and then malignant. For this reason, it is best to monitor any growth.  They can only be distinguished by HISTOPATHOLOGY  3 things are key in determining difference:  a) Borders  b) Growth rate  c) Anaplasia – lack of differentiation  ANAPLASIA  Means “Lack of Differentiation”  “Differentiation” is the extent to which neoplastic cells resemble normal tissues, both morphologically and functionally  – Well-differentiated: closely resembles tissue of origin  – Poorly-differentiated: unspecialized, little resemblance to tissue of origin  Anaplastic cells are poorly differentiated  BENIGN TUMOURS:  Encapsulated (pushing borders)  Do not invade locally  Slow growth  Mild anaplasia (well differentiated)  MALIGNANT TUMOURS:  Local Invasion – They have infiltrative borders  Rapid growth rate - Histology shows numerous mitotic figures  Anaplasia – Lack of differentiation  NOTE: Cancer - common term for malignant neoplasm  NEOPLASM NOMENCLATURE  Tumors are named according to the neoplastic component  (Cell type) + (modifier to indicate benign/malignant) + (site of origin)  Benign and malignant tumors each have their own nomenclature PRINCIPLES  I. In general, benign tumors are designated by attaching the suffix - oma to the cell type from which the tumor arises. Example: A benign tumor arising in fibrous tissue is a fibroma.  II. Malignant neoplasms arising in mesenchymal tissue or its derivatives are called sarcomas (sarcos = fleshy). Example: A malignant tumors of fibrous tissue origin is a fibrosarcoma.  Malignant neoplasms of epithelial cell origin are called carcinomas. PRINCIPLES  III. If the tumor originated in glandular epithelium, use the root adeno- (adenoma or adenocarcinoma).  If the tumor originated in squamous or transitional epithelium, is benign, and protrudes above the epithelial surface, use the root papillo- (papiloma).  If the tumor originated in non-glandular epithelium and is malignant, name it for the cell of origin. Examples: Squamous cell carcinoma (skin) Basal cell carcinoma (skin)  Malignant tumours of the blood-forming tissue are designated by the suffix -emia (Greek: “blood”).  Thus, leukemia refers to a cancerous proliferation of white blood cells (leukocytes).  Cancerous tumours that arise in lymphoid organs, such as the spleen, the thymus, or the lymph glands, are described as malignant lymphomas.  There are two main types of lymphoma:  Non-Hodgkin: Most people with lymphoma have this type.  Hodgkin EXCEPTIONS  Some “-omas” are malignant –Lymphoma –Hepatoma –Seminoma –Melanoma  Some “carcinomas” or “sarcomas” are benign --Basal cell carcinoma of skin –Cystosarcoma phyllodes of breast –Well differentiated liposarcoma of skin GRADING OF CANCERS  Malignant neoplasms are further described by the histopathologist on the degree to which the histological appearance and architecture of the tumour resembles that of the normal organ or tissue from which it was derived.  Grade: A histologic parameter quantitating the degree of differentiation of the cancer cells.  Well-differentiated (“low grade”) tumors resemble mature normal cells of the tissue of origin.  Poorly differentiated (“high grade”) tumors show little resemblance to the tissue of origin.  Many tumors graded according to a three-tiered scheme: well, moderately, and poorly differentiated (grade 1, 2, 3).  Grading systems vary by different tumor type.  Grade predicts behavior (for many common malignancies)  This information is of use in determining treatment and prognosis. Poorly differentiated (high (G3) grade) tumours usually demonstrate a more aggressive behaviour.