Cancer is a disorder caused due to accumulation of mutations in genome. Usually these mutatuions are at more than one Locus. Typically genes which are responsible for controlled growth, maturation and differentiation of the cell are affected. This causes irregular and uncontrolled growth and multiplication of the cells, where most of the cells do not mature properly and also they lack differentiation.
Such cells starts growing abnormally and starts infilterating adjecent tissues and later starts migrating to other sites through lymphatics and blood vessels and infiltrates tissues at other site in body this is phenomenon called Metastasis.
As these cells are abnormal in growth and maturation majority of the cells of same tissue have abnormally different character due to which the tissue starts functioning abnormally and can not retain its normal structure as well.
This genetic anomaly can be a germ line defect or can be acquired due to life style or enviromental insults on the genome.
Most common known causes of cancer are
Its a well established fact that tobacco in any form causes cancer, almost 20% of cancer patient have tabocco as cause of cancer.
Patient usually gets exposed to ionising radiations when he is subjected to radiological investigations for medical purpose or in region with high radioactivity due to previous contamination of the region with ionising radiation producing source or high intensity wireless communication system emitting radiations.
Non Ionising radiations
Exposure to heat of sun and its Ultra Violet radiations on regular basis for prolonged period of time, this type of exposure usually causes skin cancers like melanoma.
Cancer show strong association with obesity in its incedence and progression.
Faulty Diet high salt diet causes Gastric cancers. similarly too spice and oily diet more of processed food and maida are also associated with malignancies of gastro-intestinal system.
Certain virus causes cancer in humans like Human papiloma virus, Hepatitis B virus, Hepatitis C virus, Epstein-Barr Virus, Human T cell Leukemia virus.
Certain bacterias like Helicobacter Pylori are strongly associated with Gastric Carcinoma.
Sedentary life style
It is found that person having sedentary lifestyle with lack of exercise have shown inceased incidence and progression of cancer and vice a versa regular exercise reduces chances of cancer and in those who are affected shows regression or slowing down of progression of cancer
Now a days with industralisation air water earth food everything is polluted or adulterated with carcinogens beyond our human body’s capability to tolerate or adapt which has caused increase in incidence of cancer especially in industrailsed areas.
Exposure to benzene or other carcinogens.
Types Of Cancers Based On Cell Type
Cancer derived basically from Epithelial Cells which line the inner and oter linning of organs and they originate from endoderm, ectoderm and mesoderm
They are further divided into
Carcinoma in which microscopic features like cytology, tissue architecture, molecular products corresponds to Glandular cells and tissue pattern
Squamous Cell Carcinoma
This type of Carcinoma microscopically shows cellular differentiating features resembling to squamous epithelium.
This type of Carcinoma shows mixed pattern of Adenocarcinoma and Squamous cell carcinoma where each of the type comprises atleast 10% of tumour volume.
Undifferentiated or Anaplastic Carcinoma
These types are high grade carcinomas where there is gross lack of cytological or histological differentiation compared to other differentiated carcinomas this includes many Pseudo Sarcomatous subtypes like Sarcomatoid Carcinoma, Spindle-Cell Carcinoma, Giant-Cell Carcinoma, Pleomorphic Carcinoma. Many a times Carcinoma and true Sarocoma co-exist e.g. Carcinosarcoma and Pulmonary Blastoma.
They are smaller in sizeand have less of cytoplasm with component of polygonal or spindle shape cells.
These types of carcinomas shows excess of cytoplasm filled – Large Monotonous round or polygonal cells.
Carcinoma of Unknown Primary(CUP)
Where the lesion has transformed cells whose origin and developmental lineage is unknown but they show some typical cellular Histological and Molecular character of Epithelial Cells.
Carcinoma in Situ
Epithelial cells not cancerous but significantly abnormal to fall in transition phase but not exactly Carcinoma.
Cancer derived from Non Heamatopoeitic Messenchymal Cells that is Messenchymal Cells which are outside bone marrow
Cancer originating from Heamotopoeitic cells that arise from bone marrow and mature in Lymphnodes.
Cancer originating from Heamotopoeitic cells that arise from bone marrow and mature in Blood.
Cancer derived from precursor or intermediate cells forms and embryonic tissue.
Cancer derived from Pluripotent cells mostly present in Testes and Ovaries.
Genetics of Cancer
We can broadly divided genes involved in cancer in two types of sets viz
- Oncogene Genes – Genes Responsible for Growth Maturation and Division of cells
- Tumour Supressor Genes – Genes that inihibit the growth of cells
Any mutation in the above class of genes which alters their activity may result into transformation of normal cell into malignant cancerous cell. Typically such cells shows many mutations at various Loci.