Objective: The secondary primary malignancy frequencies have seen increased in chronic lymphocytic leukemia (CLL) regardless of therapy. The aim of this study was to investigate the frequency of secondary primary malignancy in patients followed with the diagnosis of chronic lymphocytic leukemia.

Materials and Methods: The 183 patients with diagnosed of CLL were enrolled into this study. The data of the patients were evaluated retrospectively. Patients diagnosed with CLL were categorized according to age, gender and presence or absence of additional malignancy. Patients with CLL and concomitant malignancy were compared with other patients.

Results: Fifty four patients (29.5%) were female and 129 (70.5%) were male. Secondary primary malignancy was detected in 9 (%4,9) patients. CD5 positivity was found in all of the patients with malignancy and in 91% of whole patients. 5.4% of males and 3.7% of females had solid organ tumors with CLL. Although the proportion of solid tumors was higher in males, this difference was not statistically significant (p = 0.847). The mean age of cases with secondary malignancy was statistically significantly higher than that without secondary malignancy (p <0.05).

Conclusion: In our study, all of the patients with the second primary malignancy were CD5 positive. BCL2 proto-oncogene levels were found increased in CD5-positive CLL cells, not in normal B cells those were positive for CD5. In vitro studies showed that, B-CLL cells with higher BCL2 levels survive is longer than cells with lower BCL2 levels. Presence of the secondary malignancy except CLL may be related with BCL2 increment as well as CD5 positivity. We need more comprehensive studies to determine the relationship between the presence of BCL2, CD5 positivity and secondary malignancies.