The<unk> is the effect of a growing<unk>  on surrounding structures. Examples include the consequences of growing tissue, blood or edema in a confined space. This may cause surrounding structures to shift or be compressed.
For example, cancer of the thyroid gland may cause symptoms due to compressions of certain structures of the head and neck; pressure on the laryngeal nerves may cause voice changes, narrowing of the windpipe may cause stridor, pressure on the gullet may cause dysphagia. Blood or edema in the brain may cause structures to shift.
Surgical removal or debulking may alleviate the symptoms.
Mass effect 
Cognitive bias
Lotus effect
Confounding
Length time bias
Random variable
Unblinding
Founder effect