In this research we analyzed the correlation between the emergence in the blood of patients with one of the three oncological diseases (Hodgkin’s lymphoma, non-Hodgkin’s lymphoma, multiple myeloma) of an abnormal group of cells which called the “fifth cluster” and some clinical parameters. Using a modification of the chi-square statistical criterion (Pearson criterion) to test the hypothesis of independence of two nominal features, the coefficients of mutual conjugation of Kramer and Pearson are calculated, which reflect the relationship between the considered parameters and the appearance of the cluster in the blood. The classification of these relationships is described. The results are presented in tabular form.