From the Journals

Cortactin expression aids in CLL-MCL differential



The presence or absence in tumor cells of cortactin, a cytoskeleton-remodeling adapter protein, may be a marker to help pathologists distinguish between chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL), investigators suggest.

A study of cortactin expression in tumor samples from patients with B-cell CLL, MCL, and other hematologic malignancies showed that while cortactin was present in 14 of 17 CLL samples, it was not expressed on any of 16 MCL samples, reported Marco Pizzi, MD, PhD, from the University of Padova (Italy) and his colleagues.

“In particular, cortactin may contribute to the differential diagnosis between CLL and MCL, two neoplasms with similar histological features but very different clinical outcome. Further studies are needed to clarify the molecular mechanisms of deranged cortactin expression in MCL and CLL and to investigate any possible relationship between cortactin status and the biological features of these lymphomas,” they wrote in Human Pathology.

Overexpression of cortactin has been reported in several solid tumors, and increased expression of CTTN, the gene encoding for cortactin, has been associated with aggressive, poor prognosis disease, the investigators noted.

To characterize cortactin expression in lymphoid and hematopoietic cells and detect potential associations between cortactin and virulence of hematologic malignancies, the investigators performed immunohistochemical analysis on samples from 131 patients treated at their center. The samples included 17 cases of CLL, 16 of MCL, 25 of follicular lymphoma (FL), 30 of marginal zone lymphoma (MZL), 10 of hairy cell leukemia, three of splenic diffuse red pulp small B-cell lymphomas (SDRPBL), and 30 of diffuse large B-cell lymphoma (DLBCL).

They found that cortactin was expressed in 14 of the 17 CLL samples, all 10 of the HCL samples, and 22 of the 30 DLBCL samples. In contrast, there was no cortactin expression detected in any of either 16 MCL or three SDRPBL samples. The researchers found that 13 of 30 MZL samples had low-level staining. In FL, cortactin was expressed in 2 of the samples but in the remaining 23 cases the researchers found only scattered cortactin-positive lymphoid elements of non–B-cell lineage.

The investigators also found that cortactin expression in CLL correlated with other CLL-specific markers, and found that expression of two or more of the markers had 89.1% sensitivity, 100% specificity, a 100% positive predictive value, and 90.5% negative predictive value for a diagnosis of CLL.

In addition, they saw that the immunohistochemical results were similar to those for CTTN gene expression assessed by in silico analysis.

The investigators noted that CLL and MCL are challenging to differentiate from one another because of morphologic similarities and partially overlapping immunophenotypes.

“In this context, cortactin expression would strongly sustain a diagnosis of CLL over MCL, particularly in association with other CLL markers (i.e., LEF1 and CD200),” they wrote.

The study was internally supported. The authors declared no conflicts of interest.

SOURCE: Pizzi M et al. Hum Pathol. 2018 Nov 17. doi: 10.1016/j.humpath.2018.10.038.

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