Pleural effusion of a second neoplasm in a patient with B-CLL: two immunological compartments

We report the case of a patient with a chronic lymphocytic leukemia (CLL) who later developed a metastasized large-cell neuroendocrine carcinoma of the lung that was complicated by a malignant pleural effusion. In contrast to the peripheral blood where the malignant B-CLL cells represented >99% of all lymphocytes, lymphocytes infiltrating the malignant effusion were mainly T cells. Nearly all of these T cells were CD4(+). This stood in sharp contrast to the peripheral blood where the CD4(+)/CD8(+) ratio remained balanced. A detailed analysis of the CD4(+) T cells within the malignant effusion revealed that these cells uniformly expressed a CCR7(+) CD62L(+) "non-effector" phenotype. When the monoclonal B cells within the malignant effusion were analyzed, we found that these cells, in contrast to the B-CLL cells in the peripheral blood, were negative for CD23 and expressed much higher levels of the adhesion molecules L-selectin (CD62L) and CD11a. A deficient expression of these adhesion molecules might have led to a "trapping" of the majority of B-CLL cells in the peripheral blood. This phenomenon might have contributed to the development of two highly different immunological compartments in this patient with CLL and pleural effusion of a solid tumor.