During a cancer screening a doctor may choose to screen using histological or cytological methods. Cytological methods are often less invasive than histological methods. Why do you think this may be?
Histology usually requires intact tissue gathered from a biopsy or dissection, while cytology usually looks at individual cells which can be collected without greatly disturbing the entire tissue.
Histology often requires imaging of the whole body, while cytology requires an external exam of the body without any imaging tools.
Histology involves surgery so that whole organs can be examined, while cytology can be performed using genetic or molecular analysis of bodily fluids such as saliva or urine.
Histology requires removing and analyzing single cells from an intact tissue, while cytology can be performed using imaging techniques such as MRI and therefore does not require removing cells or tissue from the body.