Abdulrahman Alhanbali. Bahaa Najjar. Maha shomaf

Transcription

1 14 Abdulrahman Alhanbali Bahaa Najjar Maha shomaf 1

2 Neoplasia In this lecture we will talk about neoplasia, its features and the nomenclature of different types of tumors. Neoplasia (neo: new and plasia: growth) is a very important topic nowadays. Neoplastic tissue is characterized by being a new abnormal growth of cells that are normally present in the body. There are some differences between neoplastic growth and normal growth such as: We know that normal cells are divided to 3 groups according to their ability to grow and divide: labile cells which are continuously dividing, quiescent cells which divide when it is needed and permanent cells that don t divide. On the other hand, neoplastic cells can divide regardless of their type. Unlike normal cells, the growth of neoplastic cells is not coordinated; they don t need a stimulus to start growing and dividing, and they don t respond to inhibitors. Neoplastic cells can escape from cell death mechanisms by different way. Those differences will lead to the accumulation of neoplastic cells forming masses commonly known as tumors. Note: tumors can be inflammatory, hyperplastic, clotting Types of neoplasm: neoplasms are classified according to their behavior to benign and malignant. -Benign tumors are localized and can t infiltrate to other tissues and that s why they can be cured by surgery and are usually incapsulated. -malignant tumors on the other hand can metastasize (infiltrate to other tissues). Malignant tumors are called cancer (the Latin word for crab) because they adhere tightly to the tissue, so it is hard to remove them by surgery. Regardless of the other differences between benign and malignant tumors, metastasis is the most differential manifestation of malignant tumors. (metastasis will be discussed in detail in the next lectures). 2

3 Some characteristics of tumor cells: Cells that make tumors are abnormal because they acquire some genetic changes(mutations). Those cells are called transformed cells. During the process of tumor progression these cells acquire more and more genetic changes and that will change the characteristics of the tumor. (e.g. some tumors are responsive to therapy in initial stages but in terminal stages they become immune to that therapy). These cells are called subclones. Tumor cells are very active cells so their nutritional needs increase; that s why tumor cells can make new blood vessels. In addition to that, tumor cells will consume all nutrients of the tissue, so the patient can be losing weight, yet the tumor is still growing rapidly. Tumors are composed of two types of cells: 1- Neoplastic cells called parenchyma. 2- the stroma: Supportive background of the tumor (connective tissue, blood vessels and inflammatory cells). Note: stroma can be the epithelial tissue in sarcoma case. Note: sarcoma mean cancer "malignant" in C.T. Nomenclature: When we want to designate a tumor, we depend on the classification of that tumor. -Tumors can be malignant or benign. -Tumors can arise from epithelial or non-epithelial tissue. -We don t depend on stroma in nomenclature because it is nearly the same for all tumors. 1- Benign tumors: a- Non-epithelial: 3

4 For naming benign tumors from non-epithelial origin we use the tissue name followed by the suffix -oma. (e.g. fibroma, lipoma etc.). -sometimes we use the Latin name of the tissue (e.g. chondroma, osteoma, hemangioma). -there are some exceptions (names that end in oma but are actually describing malignant tumors) such as: lymphoma, melanoma (melanocytes tumor), dysgerminoma (in ovaries), seminoma and all brain tumors that end with oma (neurocytoma, astrocytoma, ependymoma), also all tumors that end with blastoma (e.g. nephroblastoma). b- epithelial: we depend on the microscopic and macroscopic appearance of the tumor to name the benign tumors from epithelial origin. -a benign tumor that forms a gland is called an adenoma. However, tumors that arise from cells that secrete anything even if they didn t form a complete gland are also called adenoma (e.g. thyroid adenoma, adrenal adenoma etc.). -Sometimes in adenoma some of the glands dilate and form a cystlike structure. We call those tumors cystadenoma; these are common in ovaries. -we sometimes describe the tumor according to the gross structure such as papilloma and polyps. -papilloma and polyps are masses that project over surfaces. -a polyp is a tumor that arises from superficial epithelium forming a lump that projects over the surface (remember that this is a gross description and it is not specific like microscopic descriptions. So, to know exact type and behavior of polyp it must be resected and sent to the microscopic examination). The term polyp is commonly used in the GI tract. -papillomas are usually larger than polyps and their surfaces show some invaginations (finger-like projections over the surface of the tumor, e.g. nasal papilloma). 4

5 c-mixed tumors: tumors are usually formed from one type of cells, but some tumors are composed from more than one type and those are called mixed tumors. -a pleomorphic adenoma is a mixed tumor of the salivary gland. It is composed from epithelial and nonepithelial components. It can contain islets of bone or cartilage. -fibroadenoma is a benign mixed tumor that arises in the female breast. It is composed of epithelial ducts surrounded by nonepithelial fibrous tissue. Sometimes the fibrous tissue can outgrow the epithelial cells, so the ducts will be compressed and will appear as lines under the microscope. - Teratomas originate from totipotential stem cells such as those normally present in the ovary and testis and sometimes abnormally present in sequestered midline embryonic rests. -teratoma can contain any type of body tissues (e.g. it can contain bone, eye, hair etc). In order to differentiate whether the tumor is benign or malignant we have to look for mature tissues in the teratoma; if all the tissues are mature then the teratoma is benign, if there is an immature tissue and there are some stem cells that are capable of dividing and differentiating then the tumor is malignant. 2- Malignant tumors: a- Epithelial: Epithelial malignant tumors are called carcinoma. If the tumor is forming in a gland it is called adenocarcinoma. b- Non-epithelial: Malignant tumors originate from non-epithelial cells are called sarcomas. (e.g. fibrosarcoma, chondrosarcoma etc.). 5

6 Some masses are not considered neoplastic masses such as: -hamartoma which are malformation of the tissue that presents as a mass of disorganized tissue indigenous to the site (e.g. liver hamartoma, lung hamartoma) **note: according to the book they are considered to be neoplastic, but the doctor said they aren t. :\ -choristoma: we might find a well-developed tissue far from its original place (ectopic) those are called choristoma (e.g. Pancreatic or adrenal rest). The doctor said that the tables in the slides are very important, so you should memorize them. Now some of note: "very important" - Any mass, any swelling is tumor. - Tumor can be plastic "neoplasm" or non-plastic. - Neoplasm is clonal that's mean it comes from 1 cell من الدكتورة هيام : في عنا خلية وحدة صار فيها فصارت تنقسم كثير فبصير عنا tumor Accumulation of mutations فهاي الخلية انجنت - To say a clonal should be a parent from 1 cell - Hyperplasia can cause a tumor, but it s hyperplastic not clonal and not neoplastic. neoplasm "حميد" Benign "خبيث" Malignant 6

7 - Both are uncontrolled but malignant is more uncontrolled. - Benign, innocent, localized and usually incapsulated. - Malignant can invade and destroy adjacent structure and can metastasize "spread to distant sites". - The main characteristic of malignant is genetically unstable, so they accumulate mutations. - Benign is more genetically stable. Q) can benign transform to malignant? Benign, have a mutation and are clonal but genetically more stable " they don t accumulate more mutation. the final answer: in general, they don t but in very rare cases they do transform. ** neoplasm is autonomy: means they keep growing regardless of normal growth regulatory mechanisms. 7

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