Background:

Classical Hodgkin lymphoma shows scarce tumor Reed-Sternberg/Hodgkin cells surrounded by a dense immune microenvironment. Genetic alterations at the 9p24.1 locus result in genomic imbalances in the copy number of PD-L1/PD-L2 genes, both of them being immune response regulators.

Aim:

To characterize genomic imbalances at the 9p24.1 locus in Reed-Sternberg/Hodgkin cells and immune microenvironment in biopsies of patients with Classical Hodgkin lymphoma and correlate it with PD-L1 protein expression and disease presentation.

Material and Methods:

Paraffin embedded biopsies of 22 patients with CHL were retrospectively evaluated by fluorescence in situ hybridization using SPEC CD274/PDCD1LG2/CEN9 DNA probe. The frequency of 9p24.1 alterations, amplification, copy gain and polysomy, were determined taking into account the number of gene copies with respect to the centromere. PD-L1 protein expression was evaluated by immunohistochemistry.

Results:

All cases presented alterations in the number of copies of PD-L1 / PD-L2, which are differentiated in two groups: with amplification (32%) and without amplification (68%). The latter was subdivided into rich in gains (RG) (53%) and rich in polysomies (RP) (47%). Groups with amplification and RG were younger than the RP group (p = 0.027). The latter was not associated with bulky disease, a fact observed in 40% of patients with amplification and RG. Protein expression showed score +3 only in the latter. All RP cases presented chromosome 9 monosomy in the surrounding lymphocytes, compared to 36.4% of the other two groups.

Conclusions:

Our data contributes to the biologic characterization of CHL, of interest in the context of new therapeutic modalities. MÉD.UIS.2020;34(1):35-44

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