Overview of karyotype analysis and the STACK website. A large fraction of the karyotypes in the Mitelman Database was removed to avoid potential bias in the analysis. These included partially characterized karyotypes, multiple karyotypes from the same individual, and karyotypes that were not randomly selected in the original report. Tumor type and location were used to classify karyotypes into tumor classes, and classes with small representation (< 50 karyotypes) were removed from the dataset. An algorithm was used to reconstruct the set of aberrations leading to each remaining karyotype. Three types of statistical correlations were computed: aberration co-occurrence, association between class and aberration, and class similarity (based on their common aberrations). All computed correlations, with their P-values, are available for further investigation via our website  and are directly linked to the full description of the relevant karyotypes in the Mitelman Database. Repeating the analysis without filtering ambiguities and selected karyotypes (yielding 42,763 karyotypes, 83% of the Mitelman Database) led to essentially the same conclusions.