NEOPLASIA

Neoplasia literally means "new growth."

A neoplasm is defined as "an abnormal mass of tissue the growth of which exceeds and is uncoordinated with that of the normal tissues and persists in the same excessive manner after the cessation of the stimuli which evoked the change."

Fundamental to the origin of all neoplasms are heritable (genetic) changes that allow excessive and unregulated proliferation that is independent of physiologic growth-regulatory stimuli.

A neoplasm - a tumor, and the study of tumors is called oncology (from oncos, "tumor," and logos, "study of").

Neoplasm is divided into two types

- Benign

- Malignant

Benign

1. Microscopic and gross characteristics are considered to be relatively innocent.

2. It will remain localized.

3. Cannot spread to other sites.

4. Curable by local surgical removal.

5. Patient generally survives.

Malignant

1. The lesion can invade and destroy adjacent structures.

2. Cells are poorly differentiated.

3. Spread to distant sites (metastasize) to cause death.

4. Prognosis is very poor .

All tumors, benign and malignant, have two basic components:

1. The parenchyma, made up of transformed or neoplastic cells – determines the biologic behaviour

2. The non-neoplastic stroma is made up of connective tissue, blood vessels, and host-derived inflammatory cells.

Benign Tumors

In general, benign tumors are designated by attaching the suffix - oma to the cell type from which the tumor arises.

Fibrous tissue - fibroma Cartilaginous tissue - chondroma

Adenoma is applied to benign epithelial neoplasms producing gland patterns .

Papilloma are benign epithelial neoplasms, growing on any surface, that produce microscopic or macroscopic finger-like projections.

A polyp is an abnormal growth of tissue projecting from a mucous membrane.

Cystadenoma are hollow cystic masses; typically seen in the ovary.

Adenoma

Papilloma

polyp

Cystadenoma

Malignant Tumors

Malignant neoplasms arising in mesenchymal tissue or its derivatives are called sarcomas.

A cancer of fibrous tissue origin is a fibrosarcoma, Composed of chondrocytes is a chondrosarcoma.

Malignant neoplasms of epithelial cell origin are called carcinoma.

Carcinomas that grow in a glandular pattern are called adenocarcinomas, and those that produce squamous cells are called squamous cell carcinomas.

Most of the neoplasms are of monoclonal origin.

In some instances, however, the tumor cells may undergo divergent differentiation, creating so-called mixed tumors.

Fibroadenoma of the female breast is an example of common mixed tumor.

This benign tumor contains a mixture of proliferated ductal elements (adenoma) embedded in a loose fibrous tissue (fibroma)

Teratoma

A Teratoma is an encapsulated tumor with tissue or organ components resembling normal derivatives of more than one germ layer.

Usually, however, a teratoma will contain no organs but rather one or more tissues normally found in organs such as the brain, thyroid, liver, and lung.

A mature teratoma is typically benign and found more commonly in women, while an immature teratoma is typically malignant and is more often found in men.  

CHARACTERISTICS OF BENIGN AND MALIGNANT NEOPLASMS

1. Differentiation and anaplasia,

2. Rate of growth

1. Local invasion

2. Metastasis

Differentiation and Anaplasia

Benign neoplasms are composed of well-differentiated cells that closely resemble their normal counterparts. Eg.

- A lipoma is made up of mature fat cells laden with cytoplasmic lipid vacuoles.

• In well-differentiated benign tumors, mitoses are extremely scant in number and are of normal configuration.

Malignant neoplasms are characterized by a wide range of parenchymal cell differentiation, from well differentiated to completely undifferentiated.

Eg. well-differentiated adenocarcinomas of the thyroid may contain normal-appearing follicles.

Between the two extremes lie tumors loosely referred to as moderately differentiated.

Malignant neoplasms that are composed of undifferentiated cells are said to be anaplastic.

Lack of differentiation, or anaplasia, is considered a hallmark of malignancy.

It implies dedifferentiation, or loss of the structural and functional differentiation of normal cells.

Characteristics of Anaplastic cells –

1. Pleomorphism (i.e., marked variation in size and shape).2. Nuclei are extremely hyperchromatic (darkly stained) and larg

e. 3. The nuclear-to-cytoplasmic ratio may approach 1 : 1 instead of th

e normal 1 : 4 or 1 : 6. 4. Giant cells that are considerably larger than their neighbors may

be formed and possess either one enormous nucleus or several nuclei.

5. Anaplastic nuclei are variable and bizarre in size and shape.

6.The chromatin is coarse and clumped, and nucleoli may be large.

7. Mitoses are often numerous and distinctly atypical; sometimes appear as tripolar or quadripolar forms .

8. Loss of normal polarity.

Dysplasia

A term used to describe disorderly but non-neoplastic proliferation.

Dysplasia is encountered principally in the epithelia.

It is a loss in the uniformity of individual cells and in their architectural orientation.

Dysplastic cells exhibit considerable pleomorphism and often possess hyperchromatic nuclei that are abnormally large for the size of the cell.

Mitotic figures are more abundant than usual. Frequently the mitoses appear in abnormal locations within the epithelium.

Dysplasia

When dysplastic changes are marked and involve the entire thickness of the epithelium, the lesion is referred to as carcinoma in situ, a pre-invasive stage of cancer

Dysplasia do not necessarily progress to cancer.

Rate of Growth

Most benign tumors grow slowly.

Other influences, such as adequacy of blood

supply or pressure constraints, also may affect the growth rate of benign tumors.

Adenomas of the pituitary gland locked into the sella turcica have been observed to shrink suddenly - necrosis - as progressive enlargement compresses their blood supply.

The rate of growth of malignant tumors correlates in general with their level of differentiation. Poorly differentiated – rapid growth.

Local Invasion

A benign neoplasm remains localized at its site of origin.

It does not have the capacity to infiltrate, invade, or metastasize to distant sites.

For example, as fibromas and adenomas slowly expand, most develop an enclosing fibrous capsule that separates them from the host tissue

However, not all benign neoplasms are encapsulated. For example, the leiomyoma of the uterus

Cancer grow by progressive infiltration, invasion, destruction, and penetration of the surrounding tissue .

They do not develop well-defined capsules.

Metastasis

Metastasis is the development of secondary implants (metastases) discontinuous with the primary tumor, in remote tissues.

The properties of invasiveness and, even more so, metastasis, - is the most confirmed characteristic of a malignant tumor .

Metastasis to liver .

37Dr. Reetu Baral

Route of metastasis

Malignant neoplasms disseminate by one of three pathways:

1. Lymphatic spread,

2. Hematogenous spread.

3. Seeding within body cavities,

Lymphatic Spread

Lymphatic spread is more typical of carcinomas, whereas hematogenous spread is favored by sarcomas.

Carcinoma of the breast usually arises in the upper outer quadrant and first spreads to the axillary nodes.

sentinal lymph node

A "sentinal lymph node" is defined as the first lymph node in a regional lymphatic basin that receives lymph flow from a primary tumor.

It can be delineated by injection of blue dyes or

radiolabelled tracers.

Biopsy of sentinal lymph nodes allows determination of the extent of spread of tumor, and can be used to plan treatment.

Hematogenous spread

Hematogenous spread is the most feared consequence of a cancer.

Since all portal area drainage flows to the liver, and all caval blood flows to the lungs, the liver and lungs are the most frequently involved secondary sites in hematogenous dissemination.

42Dr. Reetu Baral

Distinction between Benign and Malignant tumors:

1. The degree of differentiation, 2. Rate of growth, 3. Local invasiveness, 4. Distant spread,5. Benign tumors resemble the tissue of origin and

are well differentiated; malignant tumors are poorly or completely undifferentiated (anaplastic).

6. Benign tumors are slow growing, whereas malignant tumors generally grow faster.