A cancer cluster is a larger than usual number of the same cancers occurring during the same time period among people who live or work near each other.  Worries about cancer clusters can begin when people notice that several relatives, friends, neighbors, or coworkers have been diagnosed with cancer. Though most suspected cancer concerns are determined not to be cancer clusters, when reported, cancer cluster concerns are taken very seriously and investigated through a systematic process to determine if science is able to provide helpful information.

The Maryland Cancer Registry at the Maryland Department of Health and Mental Hygiene (DHMH), in collaboration with the DHMH Environmental Health Bureau and the Maryland Department of the Environment, work in conjunction with local health departments to thoroughly investigate all suspected cancer concerns reported by the public.