Neoplasia and Tumor Characteristics Quiz

Neoplasia I - Session 9

• Neoplasia is a broad term encompassing all tumors, both benign and malignant.
• A tumor is a swelling of any kind, but a neoplasm specifically refers to abnormal cellular growth.
• Inflammatory and traumatic swellings are not neoplasms.
• Neoplasms persist even after the initial stimulus is removed.
• Normal cell growth is regulated by mechanisms, but neoplastic cell growth is uncontrolled.
• Benign neoplasms remain confined to the site of origin while malignant neoplasms can spread.

Objectives

• Defining tumors and neoplasia
• Differentiating benign and malignant tumors
• Understanding tumor development
• Explaining clonality
• Comparing and contrasting neoplastic and normal cells
• Describing characteristics of neoplasms
• Defining dysplasia
• Identifying different types of neoplasms

Tumor Progression

• Colon cancer development involves multiple genetic changes that lead to tumor progression.
• This progression includes steps from normal epithelium to hyperproliferative epithelium, adenoma, and eventually carcinoma.
• Specific genetic mutations, such as APC, K-ras, DCC, and p53, are directly linked to specific cancers like colon cancer.

Clonality

• Cellular changes in a neoplasm are identical, suggesting a single cell origin.
• This is referred to as a "monoclonal population."
• Initial determination of clonality was made by studying the enzyme G6PD, located on the X chromosome.

Clonality in Heterozygous Women

• In women with heterozygous G6PD, cells contain either G6PD A or G6PD B alleles.
• Neoplasms in these women consist of cells with only one type of the enzyme.
• This observation, called loss of heterozygosity, is significant in understanding cancer development.

How Neoplastic Cells Differ from Normal Cells

• Neoplastic cells deviate from normal cells by exhibiting alterations in growth control mechanisms like proliferation, apoptosis, and growth factors.
• Interactions between cells and stroma (supporting tissue) are altered in some cancers.

Growth Control

• Uncontrolled cell proliferation is a key characteristic of neoplastic cells.
• The cell cycle is accelerated, and cells may live longer, defying normal programmed cell death (apoptosis), a hallmark of cancerous cells.
• Neoplastic cells often modify their metabolism for rapid growth and can induce angiogenesis (the formation of new blood vessels) to support their growth, which is absent in normal cells

Cellular Interactions

• Normal cells have interactions to control their growth and differentiation, which are often distorted in cancerous cells.
• Interactions, such as those with basement membranes, are important for regulation in differentiation, embryogenesis, and growth.
• In malignant cells, cellular interactions, particularly those that hold cells together, are altered, leading to the invasive and metastatic spread of cancer.

Differences Between Benign and Malignant Neoplasms

• Benign tumors are typically smaller, have minimal nuclear variations, are well-differentiated, retain their specialized functions, and do not typically spread.
• Malignant tumors are typically larger, show marked nuclear variations, are poorly differentiated often losing specialized functions, and can spread infiltratively, or metastasize.

Dysplasia

• Dysplasia refers to abnormal but non-cancerous changes in cells, mainly affecting epithelial cells.
• Dysplastic changes are a pre-cancerous condition with disordered cell growth, atypia, and altered differentiation.
• Dysplasia can range from mild to severe (in-situ), which may or may not progress to cancer.
• Common sites for dysplasia are the cervix, bladder, and breast, among others.

In-Situ Malignancy

• In-situ malignancy describes an epithelial tumor that shows malignant characteristics, but has not yet invaded the underlying tissues.
• It displays malignant changes such as altered cell growth, atypia, and altered differentiation, but stops at the basement membrane.

Possible Events Related to Neoplasms

• Different types of changes from benign to dysplasia to in-situ to invasive cancer can happen.

Nomenclature of Neoplasms

• Tumors are categorized based on cell type (parenchyma) and patterns (e.g., glandular, finger-like projections) determined by gross or microscopic examination.

Types of Neoplasms

• Tumors are broadly categorized as benign or malignant.
• Benign tumors are further categorized according to the cell type.
• Malignant tumors are further categorized according to the cell type, but are classified as carcinomas, lymphomas and leukemias.