Neoplasm (Neoplasia): Characteristics, Types & Difference, Factors

What is Neoplasia?

Neoplasia literally means new growth, and a new growth formed is called neoplasm. The term neoplasm derived from the Greek word neo means new and plasma means thing formed. 

The term “tumor” was originally used for the swelling which is caused by inflammation, but nowadays 

According to British oncologist Willis definition: “A neoplasm is an abnormal mass of tissue cells, the growth of which exceeds &  is uncoordinated with that of the normal tissue cells & persists in the same excessive manner after cessation (ending) of the stimuli which evoked the change.”

In the present era, a neoplasm can be defined as a disorder or abnormalities of cell growth that is triggered by a series of acquired mutations involving an individual cell & its clonal progeny.

Microscopic components of neoplasm

There are two basic components present in the neoplasm, they are following below;

1. Parenchyma:
   •  It is made up of neoplastic cells and the nomenclature and biological behavior of the tumors are mainly based on this component of the tumor.
2. Stroma 
   • Supporting cell, non-neoplastic tissue which is derived from the host. 
   • It is important for the growth, survival, & replication of tumor cells.
   • The components of the stroma include connective tissue, blood vessels, and inflammatory cells include lymphocytes and macrophages.

Characteristics of benign and malignant neoplasm

The benign and malignant neoplasms can be distinguished on the basis of the following four features;

• Differentiation and anaplasia
• Rate of growth
• Local invasion 
• Metastasis

Differentiation and anaplasia

Differentiation 

It is defined as the extent to which neoplastic parenchymal cells resemble their corresponding normal parenchymal cells of origin, both morphologically and functionally. It helps to determine the grade of the tumor.

Anaplasia

It is defined as the lack of differentiation is known as anaplasia. The meaning of anaplasia is “to form backward/backward formation’”, which means a reversal of differentiation of the cell to a more primitive level. The microscopic features of anaplasia are the following

• Pleomorphism -variation in the size and shape of cells & cell nuclei. 
• Abnormal nuclear morphology 
• Nuclear cytoplasmic (N: C) ratio: in the normal cell, the N: C ratio is 1:4 or 1:6 but in the case of malignant cells is 1:1.
• Loss of polarity 
• Growth pattern
• Bizarre cells, including tumor giant cells
• Necrosis & apoptosis

Rates of growth

There are the following factors that help to determine the rate of growth;

• Degree of differentiation
• Dependency(hormonal stimulation and adequacy of blood supply) 
• The balance between the production of the cells and loss of the cells

Local invasion

In the benign tumors;

• No invasion or infiltration and localized
• Encapsulated which is derived from connective of the native tissue
• The capsule makes a discrete, well-circumscribed, easily palpable mobile mass of the tumor and which is surgically encapsulated. 
• The capsule may be lacking in some tumors.

In the malignant tumors

• Locally invasive with the destruction of surrounding tissue in the tumor
• Poorly demarcated from surrounding tissue with margin is irregular. 
• Slow growing is pseudo encapsulated or pushing margin infiltrating adjacent tissue but surgically difficult to remove the tumor.

Metastasis

The spread of a tumor to a distant site, physically discontinuous with the primary tumor. Most cancer tissue cells have the capacity to metastasize. The larger & undifferentiated rapidly growing are more likely to metastasize. The most incurable in nature.

Pathway of spread

1. Seeding of body cavities and surfaces, for example, ovarian tumor seeding over the peritoneal surface.
2. Lymphatic pathway
   • Carcinoma is more common and regional lymph nodes involved.
3. Hematogenous pathway
   • Sarcomas but also carcinomas
   • Usual initial involvement-liver, lung

Predisposing factors of neoplasm

• Geographic and environmental factors
• Age
• Genetic factors
• Acquired predisposing conditions

Geographic and environmental factors

In geographic variation

• Stomach carcinoma is seven to eight times higher in Japan than in the US.
• Developed countries prostate tumor in the case of the male whereas breast tumor in the case of female.
• In developing countries, liver and stomach tumors in the case of men and in the case of female breast cancer is more common but less incidence than in developed countries.

Environmental factors

• Exposure to carcinogens
  • Occupational exposure-asbestosis-mesothelioma
  • Diet (colorectal carcinoma), alcohol(liver, esophagus, etc), cigarette smoking
  • Infections such as HPV infection and cervical cancer
  • Radiation 
  • Chemical agents
• Obesity 
• Reproductive history: exposure to estrogen stimulation breast & endometrial cancer

Age

• Cancer is commonly in the elderly age group more than 55 years
• The common neoplasms of infancy and childhood
  • Leukaemias
  • Primitive tumors of CNS for example, small round blue cell tumors (retinoblastoma)

Genetic factors 

The hereditary factors and three categories such as;

1. Autosomal dominant inherited cancer syndrome-inheritance of the single mutant gene, for example, RB gene in retinoblastoma and osteosarcoma. 
2. Autosomal recessive syndromes of defective DNA-repair
3. Familial cancers, for example, breast cancer

Acquired predisposing factors conditions

• The clinical conditions prone to develop into cancer include;
  • Chronic inflammations
  • Precursor lesions
  • Immunodeficiency states of conditions
• Fertile soil for malignant transformation
• Proliferating cells at risk for accumulating genetic lesions is called carcinogenesis.

Acquired predisposing conditions: immunodeficiency states

• Deficits in T-cell immunity that leads to increased risk for cancers
• Caused by oncogenic viruses
  • Lymphoma, e.g. EBV – lymphomas
  • Carcinomas, e.g. HPV- cervical carcinoma
  • Sarcoma- KSHV- Kaposi sarcoma

Difference between benign and malignant neoplasm