Cancer cluster Cancer cluster is a term used by epidemiologists , statisticians , and public health workers to define an occurrence of a greater-than-expected number of cancer cases within a group of people in a geographic area over a period of time 1 . Historical examples of work-related cancer clusters are well documented in the medical literature . Notable examples include : scrotal cancer among chimney sweeps in 18th century London , osteosarcoma among female watch dial painters in the 20th century , skin cancer in farmers , bladder cancer in dye workers exposed to aniline compounds , and leukemia and lymphoma in chemical workers exposed to benzene 2 . Cancer cluster suspicions usually arise when members of the general public report that their family members , friends , neighbors , or coworkers have been diagnosed with the same or related cancers . State or local health departments will investigate the possibility of a cancer cluster when a claim is filed 3 . In order to justify investigating such claims , health departments conduct a preliminary review . Data will be collected and verified regarding : the types of cancer reported , numbers of cases , geographic area of the cases , and the patients clinical history . At this point , a committee of medical professionals will examine the data and determine whether or not an investigation ( often lengthy and expensive ) is justified 4 . In the U.S. , state and local health departments respond to more than 1 , 000 inquiries about suspected cancer clusters each year . It is possible that a suspected cancer cluster may be due to chance alone , however , only clusters that have a disease rate that is statistically significantly greater than the disease rate of the general population are investigated . Given the number of inquiries it is likely that even some of these are due to chance alone . A cluster is more likely to be `` genuine '' if the case consists of one type of cancer , a rare type of cancer , or a type of cancer that is not usually found in a certain age group . Between 5% to 15% of suspected cancer clusters are statistically significant [ citation needed ] . See also Biostatistics Incidence List of cancer clusters Risk assessment Toxicology Notes Note 1 : Cancer Cluster FAQ . Centers for Disease Control and Prevention , National Center for Environmental Health , Division of Environmental Hazards and Health Effects . Note 2 : Cancer Facts . National Cancer Institute . U.S. National Institutes of Health . Note 3 : M. J. Thun and T. Sinks . Understanding Cancer Clusters . CA Cancer J Clin 2004 ; 54 : 273-280 Note 4 : J.R. Devier , R.C. Brownson , J.R. Bagby Jr. , G.M. Carlson , J.R. Crellin . A public health response to cancer clusters in Missouri . Am J Epidemiol 1990 ; Jul ; 132 : S23-31 . External links Cancer Mortality Maps & Graphs : U.S. , 1950-94 National Institute of Environmental Health Sciences ( NIEHS ) U.S. Centers for Disease Control U.S. Environmental Protection Agency All About Cancers Categories : Articles with unsourced statements | Oncology | Epidemiology 1 2 3 4 1 2 3 4 