Lecture 16 (P) PDF - Benign Vs Malignant Tumors

Characteristics of Benign versus Malignant Tumors Four fundamental rules by which benign tumors can be distinguished from malignant tumors: 1. Differentiation & Anaplasia (completed in last lecture) 2. Rate of growth 3. Local invasion 4. Metastasis Rules to differentiate benign fr...

Characteristics of Benign versus Malignant Tumors Four fundamental rules by which benign tumors can be distinguished from malignant tumors: 1. Differentiation & Anaplasia (completed in last lecture) 2. Rate of growth 3. Local invasion 4. Metastasis Rules to differentiate benign from malignant tumors 2-Rate of Growth Benign tumors grow slowly Malignant tumors grow faster ◦ Rate of growth correlates with the level of differentiation ◦ Poorly differentiated tumors tend to grow faster ◦ Growth is also effected by hormones and blood supply Rules to differentiate benign from malignant tumors 3- Invasion Local Invasion: Benign tumors remain localized and do not invade (encapsulated), or metastasize. Malignant tumors invade locally and metastasize. Local invasiveness is the second reliable feature to distinguish malignant from benign tumors Benign Malignant Adenoma surrounded by thin white capsule  Breast mammogram Benign Malignant Benign: Adenoma Malignant: Adenocarcinoma Rules to differentiate benign from malignant tumors 4-Metastasis ◦ Spread of the tumor to distant sites of the body ◦ Primary site: where tumor has started ◦ Secondary site: where neoplastic cells migrate and grow as a separate tumor ◦ The more anaplastic, rapidly growing and larger the primary tumor, the more likely is metastatic spread Metastasis marks a tumor as malignant Methods of metastasis include: Seeding of body cavities and surfaces: from surface of one organ to another within body cavities. e.g. ovarian Ca to peritoneum Lymphatic spread: more typical of Carcinoma Hematogenous spread: more typical of Sarcoma ◦ Arteries are penetrated less readily than veins. ◦ With venous invasion, the blood-borne cells follow the venous flow draining the site of the neoplasm often stopping at the first capillary bed they encounter. Seedling along body cavities Methods of Metastasis  Clinical significance Sentinel Lymph Node: First lymph node in regional lymphatic basin that receives lymph flow from the primary tumor Biopsy from the sentinel lymph node is used to assess for the presence or absence of metastatic deposits and therefore helps in planning for surgical treatment. - e.g. if axillary sentinel lymph node is negative for metastatic deposits, then axillary lymph nodes excision is not necessary when doing mastectomy for breast cancer. Metastasis via embolism All portal area drainage flows to the LIVER, and All caval blood flows to the LUNGs. Liver and Lungs are the most frequent sites of metastasis Metastasis to liver  Summary: Benign VS Malignant tumors Benign Malignant Compress surrounding Infiltrate surrounding tissue Gross tissue Have indiscrete borders Encapsulated No capsule formed Individual cells infiltrate Uniform population surrounding tissue No anaplasia Invade lymphatic/blood vessels No invasion/infiltration Can display anaplasia Histology Few mitotic figures Can show lack of differentiation Capsule (not always) Numerous mitosis Circumscribed Boundaries ill-defined Chromosomal aberrations Epidemiology ◦ Epidemiologic studies relate particular environmental, racial (possibly hereditary), and cultural influences to the occurrence of specific neoplasms. ◦ For instance the concept that cigarette smoking is causally associated with lung cancer arose primarily from epidemiologic studies ◦ Epidemiology provides insight into the magnitude of the cancer problem by studying cancer incidence, prevalence , mortality, age, sex and geographic differences 19  Cancer Incidence ◦ The number of new cases of specific cancer registered over a specific period in a defined population. (Adapted from Jemal A, Siegel R, Xu J, Ward E: Cancer statistics, 2010. CA Cancer J Clin 60:277–300, 2010.) 20 Saudi Health Council, 2013  Mortality ◦ The number of deaths from a given form of cancer during a specified period of time. (Adapted from Jemal A, Siegel R, Xu J, Ward E: Cancer statistics, 2010. CA Cancer J Clin 60:277–300, 2010.) 23 Cancer Prevalence Number of all cases of cancer, both new and registered within a defined population at a given point in time. Cancer, a pandemic! Cancers are among the leading causes of morbidity and mortality worldwide 25 Cancer a Pandemic 12 million deaths, 2012, WHO 70% of cancer deaths, low income countries Cancer a Pandemic 12 million deaths, 2012, WHO 1 in 3 people will 70% of cancer 1 in 6 deaths are develop cancer, deaths, low income due to cancer CRUK countries