Overview of neoplasm

Definition

A mass of tissue formed as a result of abnormal, excessive, uncoordinated, autonomous, and purposeless proliferation of cells even after removal of stimulus. 

• Neoplasm is a term while neoplasia is a process. 
• Tumour have two components, one is parenchyma (neoplastic cell) and second is stroma (supporting cells and vessels).

Limitations of definition - 

1. In most of the cases growth persists after removal of stimuli.
2. In lot of cases we may not be able to recognize initiating stimuli.

Difference between Neoplasia and Hyperplasia
Features	Neoplasia	Hyperplasia
Proliferation	Uncontrolled	Under controlled
Coordination with surrounding tissue	Uncoordinated	Coordinated
Proliferation after removal of stimulus	Persists	Stop
Differentiation	Varies	Well-differentiated

CLASSIFICATION

Classification of tumour on the basis of type of origin:

The suffix '-oma' is added to the end of the word denote benign tumour such as lipoma, fibroma, myxoma etc. but their are some exceptions also available such as haematoma, granuloma (both are not a tumour), hamartoma and choristoma. There is one thing remember adenoma derived from gland but may or may not show glandular structure e.g. tumour of the adrenal gland or cortex and renal tubular cell these are glandular origin but may or may not show glandular structure.

Malignant tumours of epithelial origin are called carcinomas, while mesenchymal origin of malignant tumour is mostly denote by the adding of word 'sarcoma' (sarcos = fleshy) such as liposarcoma, fibrosarcoma, chondrosarcoma etc. 

Classification of tumour on the basis of cell of origin
No.	Tissue of origin	Benign	Malignant
A. Epithelial tissue
1.	Squamous epithelium	Squamous cell papilloma	Squamous cell (epidermoid) carcinoma
2.	Transitional epithelium	Transitional cell papilloma	Transitional cell carcinoma
3.	Glandular epithelium	Adenoma	Adenocarcinoma
4.	Basal cell layer skin	----	Basal cell carcinoma
B. Connective tissue
6.	Adipose tissue	Lipoma	Liposarcoma
7.	Fibrous tissue (adult)	Fibroma	Fibrosarcoma
8.	Fibrous tissue (embryonic)	Myxoma	Myxosarcoma
C. Skeletal tissue
9.	Cartilage	Chondroma	Chondrosarcoma
10.	Bone	Osteoma	Osteosarcoma
D. Muscular tissue
11.	Smooth muscles	Leiomyoma	Leiomyosarcoma
12.	Skeletal muscles	Rhabdomyoma	Rhabdomyosarcoma
E. Nervous tissue
13.	Nerve sheath	Neurilemmoma, neurofibroma	Neurogenic sarcoma
14.	Nerve cells	Ganglioneuroma	Neuroblastoma
F. Mixed tumour
15.	Salivary glands	Pleomorphic adenoma	Malignant mixed salivary tumour
G. Tumours of more than one germ cell layer
16.	Totipotent cells in gonads in embryonal rests	Mature teratoma	Immature teratoma

Classification of the basis of Clinical Features: 

One is Benign and second is Malignant.

Contrasting features of Benign and Malignant tumour:

Contrasting features of benign and malignant tumour
No.	Features	Benign	Malignant
I.	Clinical and Gross features
1.	Boundaries	Encapsulated (spherical or ovoid in shape)	Irregular
2.	Surrounding tissue	Often compressed	Often invaded
3.	Size	Small	Larger
4.	Secondary changes	Less	More
II.	Microscopic features
1.	Pattern	Usually resembles the tissue of origin closely	Often poor resemblance to tissue of origin
2.	Basal Polarity	Retained	Lost
3.	Pleomorphism	Usually absent	Present
4.	Nucleo-cytoplasmic ratio	Normal (1:5)	Increased (1:1)
5.	Anisonucleosis	Absent	Present
6.	Hyperchromatism	Absent	Present
7.	Mitoses	Typical mitoses	Atypical and abnormal mitoses
8.	Tumour giant cells	May be present but without nuclear atypia	Present with nuclear atypia
9.	Function	Usually well-maintained	May be retained, lost or become abnormal
III.	Growth rate	Slow	Rapid
IV.	Local invasion	Compresses the surrounding tissue without invading	Infiltrate and invade the adjacent tissue
V.	Metastasis	Absent	Present
VI.	Prognosis	Local complications	Death by local and metastatic complications

CHARACTERISTICS OF TUMOURS

1. Rate of Growth

2. Cancer Phenotype and Stem Cells

3. Clinical and Gross Features

4. Microscopic Features

5. Spread of tumours