"Mass effect is a general concept in pathology and radiology. Whilst it is most commonly encountered in the intracranial setting 1, it is certainly not restricted to the CNS. It can be used to describe any lesion in the body if it exerts displacement of adjacent structures, for example a musculoskeletal, abdominal or pelvic mass 2-4. Some have said that if a lesion does not cause significant displacement of adjacent anatomical structures then it does not warrant the use of the term "mass"."