Metastasis
மெட்டாஸ்டாஸிஸ்
A benign tumor is a nuisance; a malignant tumor is a death sentence. The difference lies in one biological mechanism: Metastasis. If you confuse 'contact inhibition' with 'metastasis' in the exam, you have already lost the seat.
The idea
Metastasis is the defining property of malignant tumors. Neoplastic cells detach from the primary tumor mass. They enter the circulatory system, travel through blood or lymph, and colonize distant organs. This secondary tumor formation makes the disease systemic and lethal.
Why it matters
This allows cancer cells to colonize other organs, making the disease systemic and significantly harder to treat.
NEET lens
NEET asks this 8 times in the last decade. Focus on the keyword 'distant sites' and 'blood/lymph'. Do not confuse this with 'Contact Inhibition' which is the loss of property in cancer cells. Memorize: Metastasis = Malignant = Systemic spread.
Clinical significance
Metastasis represents the total failure of the body's immune surveillance. When cancer cells escape the primary site, the disease transitions from localized to systemic. This is why late-stage carcinoma is clinically difficult to treat; the tumor is no longer a single target.
Introduction
Metastasis is the spread of cancer cells from the original tumour to distant parts of the body. It is the most feared property of malignant tumours.
Core concept
Normal cells show contact inhibition — contact with other cells stops their growth. Cancer cells lose this property, divide uncontrollably and form masses called tumours. Benign tumours stay confined to their original location and cause little damage. Malignant tumours are masses of proliferating neoplastic (tumour) cells that grow very rapidly, invade and damage surrounding normal tissues, and starve normal cells by competing for vital nutrients. Cells sloughed from such tumours reach distant sites through blood, and wherever they get lodged they start new tumours — this is metastasis.
Go deeper
Because cancer can spread through blood and lymph, early detection matters: biopsy, histopathology, blood and bone-marrow tests, radiography, CT, MRI and molecular tests for cancer-related genes are used.
From Class 10
Some cancers can spread from the first tumour to other organs through the blood — doctors call this metastasis.