Neoplasia

Means a new growth Or "neoplasm". In clinical practice, called a tumour. This is not strictly correct, since the

term tumour refers to all swellings, e.g. inflammation, haematoma etc., but it is so generally accepted .

Oncology (Greek oma = tumour) Is the science of studying neoplasms

Definition

Neoplasm is an abnormal new growth, of cells independent of physiologic growth stimuli (autonomous).

Its presence serves no useful purpose Its growth is uncoordinated with that

of the surrounding tissue Its growth persists after cessation of

the stimuli which provoked its formation

In neoplasia proliferation, differentiation and organisation are all disturbed

Proliferation: a neoplasm is characterized by partial or complete loss of regulation of mitosis and cell maturation

Differentiation reduction or deletion of the specialized function of the cells

Organization loss of the morphologic tissue and organ characteristics.

Classification of neoplasms

According to their clinical behaviour into: Benign tumours, which usually grow slowly

and do not interfere with the person's well being or shorten his life, unless the tumour encroaches on a vital organ e.g. the brain or produces harmful substances e.g. excess hormones.

Malignant tumours generally are more rapidly growing, destroy and infiltrate the normal structures and unless effectively treated interfere with health and eventually cause death.

All tumours, benign and malignant are formed of

two basic components:

1- Parenchymal neoplastic cells, (proliferating neoplastic cells)

2- Supportive stroma of connective tissue and blood vessels and possibly lymphatics

Classification of tumours

1. Benign: Epithelial Mesenchymal Germ cell tumours

2. Malignant: Epithelial Mesenchymal Germ cell tumours

Classification of Tumours

A-Tumours of epithelial origin1-Str. Sq. epithelium Squamous cell papilloma. Squamous cell

carcinoma. 2-Glandular epithelium Adenoma Adenocarcinoma 3-Neuroectoderm Nevus Malignant

melanoma

B-Tumours of Mesenchymal originMalignant=sarcoma Benign=oma

Fibroma ( benign tumor of fibroblasts) Lipoma ( benign tr of lipocytes) Leiomyoma ( benign tr of smooth

muscle fibers) Rhabdomyoma( benign tr of striated

muscle fibers) Osteoma ( benign tr of osteoblasts) Chondroma ( benign tr of chondrocytes) Angioma ( benign tr of endothelium)

C- Tumours derived from more than one germ layer (from totipotential cells)

Teratoma (mature) Immature teratoma

Characterization of benign and malignant tumours

1- Capsulation

Benign tumours grow by expansion leading to pressure atrophy of the surrounding tissue with formation of a fibrous capsule. Though not all benign tumours are encapsulated, but there is always a plane of cleavage around the tumours.

Malignant tumours grow by an infiltrative manner that destroys and penetrates the surrounding tissue; they do not develop a capsule. The infiltration tends to occur in anatomic planes of cleavage

Comparison between a benign tumor of the myometrium (leiomyoma) and a malignant tumor of similar origin

(leiomyosarcoma).

Benign tumor

Capsule

Uterine leiomyoma

Malignant tumor

Malignant tumor

2 -Differentiation and anaplasia

Differentiation refers to the extent to which the tumour cells resemble their normal counterpart, both morphologically and functionally

Benign neoplasms are composed of well-differentiated cells that resemble very closely their normal counterpart e.g. lipoma. Mitoses are extremely scant in number and are normal in configuration.

Follicular adenoma thyroid

Malignant tumours are characterized by a wide range of parenchymal differentiation from surprisingly well-differentiated to those completely undifferentiated.

Well differentiated adenocarcinoma colon

Poorly differentiated carcinoma

Anaplasia: Definition

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

eg. Malignant tumours formed of undifferentiated cells are called anaplastic tumours,

anaplasia is a marker of cancer.

The following cytologic features characterize malignant cells:

Nuclear and cellular pleomorphism: wide variation in the shape and size of cells and nuclei.

Hyperchromatism: darkly-stained nuclei that frequently contain prominent nucleoli.

Nucleo-cytoplasmic ratio: approaches 1:1 instead of 1:4 or 1:6 reflecting enlargement of nuclei.

Abundant mitoses: reflect proliferative activity. Mitotic figures may be abnormal (atypical e.g. tripolar, quadripolar or multipolar spindles).

Tumour giant cells: containing a single large polypoid nucleus or multiple nuclei.

Anaplastic tumours also demonstrate a total loss of tissue architecture e.g. in an anaplastic tumour of uterine cervix, the normal orientation of squamous epithelial cells with respect to each other is lost (loss of polarity).

Well-differentiated tumours, whether benign or malignant, tend to retain the functional characteristics of their counterparts such as the production of hormones in tumours of endocrine origin or keratin in squamous epithelial tumours. Anaplastic tumours have no specialized functional activity.