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.

ContentsDefinition

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

1. Excessive cellular proliferation;

2. Lack of responsiveness to control mechanisms;

3. Lack of dependence on the continued presence of the

stimulus.


The gross appearance of tumor is varied. It is

usually related to histogenesis, site and biologic

behavior.


Gross appearance of tumor-shape:

a. polypoid

b. papillary

c. nodular

d. lobulated

e. cystic

f. fungating

g. ulcerated


lipoma

Hepatocellular carcinoma

Color of tumor:


Two basic components of all the tumors:

1. 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.

2. 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.

NomenclatureBenign tumors: “ ~ oma”, e.g., fibroma; lipoma

Malignant tumors: “ ~ carcinoma, ~ sarcoma”

thyroid adenoma colonic adenoma

leiomyoma of uterus fibroadenoma of breast

heptocellular carcinoma

Squamous cell carcinoma adenocarcinoma of colon

osteosarcoma of bone


Neoplasm differentiation denotes the degree to which a

neoplasm cell resembles the normal mature cells of the

tissue both morphologically and functionally.

What is neoplasm differentiation?


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.


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 .

What is anaplasia?


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.

Rate of growth and malignancy:


Nearly all benign tumors grow as cohesive expansile

masses that remain localized to their site of origin.

a. 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.

b. When a benign tumor arises in a epithelial or mucosal

surface, the tumor grow away from the surface, often

forming a polypoid.

Invasion ( Infiltration)

LipomaHere 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).


The growth of cancers, in contrast, is accompanied by

infiltration, invasion, and destruction of the

surrounding tissue.

a. 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.

b. Malignant tumors on epithelial or mucosa surface may

form a protrusion in the early stages, but eventually

invade the underlying normal tissue.

Invasion ( Infiltration)

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.

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.

Metastasis

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.

What is metastasis of neoplasms?

Metastasis

1. Lymphatogenous metastasis- The most common

pathway for initial dissemination of carcinomas, but

sarcomas may also use this route.

2. Hematogenous metastasis- This route is typical of

sarcomas but is also seen with carcinoma..

3. Metastasis in body cavities ( seeding )- Direct

seeding of body cavities or surface (exfoliation and

implantation on peritoneum, pleura, subarachnoid)

Routes of metastasis

characteristics Benign MalignantDifferentiation 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

A premalignant or precancerous lesion is an

abnormality in a tissue area which is a just a step

away from cancer.

a. Not all precancerous lesions change to cancer, but

most have potential to become malignant.

b. It is important to recognize precancerous lesions

because surgical excision is curative.

What is precancerous lesions?

Table 5-5 page114

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:

a. Increased size of the nucleus, (absolute and relative to the amount of cytoplasm)

b. Hyperchromatism

c. Abnormal chromatin distribution (coarse clumping)

d. Nuclear membrane is thickneng and wrinkling.

e. In squamous epithelium, mitotic figures appear in many layers.

What is dysplasia?

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.

What is carcinoma in situ?

Chapter 5 Neoplasia

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