Chapter 5 Neoplasia

Background The tumor is a common disease all over the world. In many countries especially developed countries, malignant tumor has become the first or second leading cause of death. Although many research works focused on oncology and great progress has been made in understanding tumors in the past decades, the morbidity and mortality rate of malignant tumor is increasing. The underlying causes include air pollution, pressure, excess weight, unhealthy lifestyle, ageing population and so on.

Contents Definition Structure Characteristics of Tumors Nomenclature Differentiation and Anaplasia Growth, Local Invasion and Metastasis Difference Between Benign and Malignant tumors Effects of Tumors on the Hosts Precancerous Lesions, Dysplasia, and Carcinoma in situ Brief Introduction of Common Neoplasms

Definition of Neoplasm A neoplasm is an abnormal mass of tissue, it’s growth exceeds and is uncoordinated with that of the normal tissue and persist in the same excessive manner after cessation of the stimuli which evoke the change. (Dr. RA Willis)

Definition of Neoplasm At molecular level, neoplasm is disorder of growth regulatory genes ( the activation of proto- oncogenes and the inactivation of tumor suppressor genes ). It develops in a multistep fashion, such that different neoplasms, even of the same histological type, may show different genetic changes.

Features of Neoplasm Excessive cellular proliferation; Lack of responsiveness to control mechanisms; Lack of dependence on the continued presence of the stimulus.

Structure Characteristics of Tumors The gross appearance of tumor is varied. It is usually related to histogenesis, site and biologic behavior.

Structure Characteristics of Tumors Gross appearance of tumor-shape: polypoid papillary nodular lobulated cystic fungating ulcerated

Structure Characteristics of Tumors Color of tumor: lipoma Hepatocellular carcinoma

Structure Characteristics of Tumors Two basic components of all the tumors: Parenchyma – the parenchyma is made up of proliferating neoplastic cells and largely determines the biologic behavior of the tumor. In addition, the classification, nomenclature and histological diagnosis are also made according to the parenchymal cells. Supporting stroma – the supporting stroma is made up of connective tissue, blood vessels, and possibly lymphatics.

parenchyma supporting stroma

Nomenclature Basic principle: Neoplasms are named according to binomial system denoting their histogenic origin of the parenchymal component and the biologic behavior.

Nomenclature Benign tumors: “ ~ oma”, e.g., fibroma; lipoma Malignant tumors: “ ~ carcinoma, ~ sarcoma”

fibroadenoma of breast thyroid adenoma colonic adenoma leiomyoma of uterus fibroadenoma of breast

osteosarcoma of bone heptocellular carcinoma Squamous cell carcinoma adenocarcinoma of colon osteosarcoma of bone

Differentiation and Anaplasia What is neoplasm differentiation? Neoplasm differentiation denotes the degree to which a neoplasm cell resembles the normal mature cells of the tissue both morphologically and functionally.

Differentiation and Anaplasia Benign tumors are usually well differentiated. They resemble closely their normal counterpart. Malignant tumors, on the other hand, show variable degree of differentiation. Malignant tumors that are composed of undifferentiated cells are said to be “anaplastic”,that means no morphological resemblance to normal tissue.

Differentiation and Anaplasia What is anaplasia? lack of differentiation; literally means ‘to form backward,’ implying a ‘reverse differentiation’ of mature normal cells. For cancers, it does not represent reverse differentiation. It means lack of differentiation .

Growth, Local Invasion and Metastasis Rate of growth and malignancy: The growth rate of neoplastic cells varies greatly and is one of its chief factors that serves to distinguish benign from malignant. In a general rule, the degree of malignancy of a neoplasm is correlated with its growth rate: the more rapid the growth, the more malignant the neoplasm.

Growth, Local Invasion and Metastasis Invasion ( Infiltration) Nearly all benign tumors grow as cohesive expansile masses that remain localized to their site of origin. Benign tumors grow slowly and usually develop a fibrous capsule keeping the tumor as a discrete, readily palpable and easily movable mass that can be excised. When a benign tumor arises in a epithelial or mucosal surface, the tumor grow away from the surface, often forming a polypoid.

Lipoma Here is a benign lipoma on the serosal [si'rəusəl] surface of the small intestine. It has the characteristics of a benign neoplasm: it is well circumscribed, slow growing, and resembles the tissue of origin (fat).

Growth, Local Invasion and Metastasis Invasion ( Infiltration) The growth of cancers, in contrast, is accompanied by infiltration, invasion, and destruction of the surrounding tissue. In general, malignant tumors are lack of a well defined cleavage plane and usually exhibit local invasiveness or infiltration that make it difficult to be excised. Malignant tumors on epithelial or mucosa surface may form a protrusion in the early stages, but eventually invade the underlying normal tissue.

Squamous cell carcinoma of lung Malignant neoplasms are also characterized by the tendency to invade surrounding tissues. Here, a lung cancer is seen to be spreading along the bronchi into the surrounding lung.

hepatocellular carcinoma hepatic adenoma hepatocellular carcinoma Here is a small hepatic adenoma that shows how well-demarcated an benign neoplasm is. In contrast, this hepatocellular carcinoma is not as well circumscribed (note the infiltration of tumor off to the lower right) nor as uniform in consistency. It is also arising in a cirrhotic (nodular) liver. cirrhotic[si‘rɔtik] 肝硬化

Metastasis What is metastasis of neoplasms? Metastasis is to form a second neoplastic mass through transfer of the neoplastic cells from the first neoplasm to a distant site on separate from the original tumor.

Metastasis Routes of metastasis Lymphatogenous metastasis- The most common pathway for initial dissemination of carcinomas, but sarcomas may also use this route. Hematogenous metastasis- This route is typical of sarcomas but is also seen with carcinoma.. Metastasis in body cavities ( seeding )- Direct seeding of body cavities or surface (exfoliation and implantation on peritoneum, pleura, subarachnoid) The routes of malignant tumors metastasis include Lymphatogenous metastasis- Metastasis via the lymphatic usually occurs in carcinoma and melanoma. For sarcomas, they tend to spread mainly via the blood stream. Malignant cells are carried by the lymphatic to the regional lymph nodes. The brief that cancerous cells spread first to the regional nodes is rationale for radical surgery. So, clinician should get hold of the lymphatic drainage of various tissues to predict the most likely sites of lymph nodes involvement. Hematogenous metastasis- Entry of cancerous cells into the bloodstream is believed to occur in the early clinical course of many malignant neoplasms. Some types of cancer apparently favor particular metastatic sites. For example, skeletal metastases are common in cancer of prostate, thyroid, lung, breast, and kidney. Adrenal metastases are common in lung cancer. But the mechanisms responsible are unknown. Metastasis in body cavities ( seeding We will discuss all the three points one by one.

Benign Malignant characteristics Differentiation Well differentiated Range from well differentiate to undifferentiated Rate of growth Slow growth over a period of years Rapid growth, sometimes erratic Type of growth Expansile Progressive infiltration, invasion, and destruction of surrounding tissue Separated from Yes, has fibrous capsule composed of stroma of native tissue Poorly separated Metastasis No Yes Effect on host Often insignificant Significant, fever, anemia, infections, etc. Recurrence Rare Often Cell shape Monomorphic Pleomorphic Tumor giant cells Nuclear chromatin Normal Inreased, hyperchromatic; Peripheral clumping Nucleoli Not prominent Prominent, irregular shape

Precancerous Lesions What is precancerous lesions? A premalignant or precancerous lesion is an abnormality in a tissue area which is a just a step away from cancer. Not all precancerous lesions change to cancer, but most have potential to become malignant. It is important to recognize precancerous lesions because surgical excision is curative. Table 5-5 page114

Dysplasia What is dysplasia? Dysplasia is an abnormality of both differentiation and maturation. This term should be restricted to abnormalities of cell growth with the characteristics as following: Increased size of the nucleus, (absolute and relative to the amount of cytoplasm) Hyperchromatism Abnormal chromatin distribution (coarse clumping) Nuclear membrane is thickneng and wrinkling. In squamous epithelium, mitotic figures appear in many layers.

Carcinoma in situ What is carcinoma in situ? The term carcinoma in situ refers to an epithelial neoplasm exhibiting all the malignant cellular features. But it has not yet invaded with through the epithelial basement membranes separating it from potential route of metastasis. It is only at this very early stage the excision of the tumor will guarantee a cure. So detection of carcinoma in situ is very important. In clinical practice, detection of carcinoma at the in situ stage, or detection of precancerous lesions is the aim of population screening programs for cervical, breast and some other carcinoma. Through these popular screening, many lives have been saved.