A new methodological approach in the diagnosis of extra-medullary lymphomas: the role of classical and molecular cytogenetics.

Lymphomas are a group of heterogeneous malignant neoplasms involving B, T and NK lymphocytes. Their localization is predominantly lymph node, but frequently they can diffuse to the bone marrow. Cytogenetic analysis, required for a correct diagnosis, prognosis and therapy is harder when the lymphoma is extra-medullary: in these cases Fluorescence In Situ Hybridization (FISH) analysis is commonly applied, performed on interphase nuclei coming from sections of lymph node tissue. However, this method has some limitations: 1) it is based on the use of locus specific probes and it provides targeted information; 2) the outcome of FISH investigations is strongly conditioned by the correct processing of the biopsy sample and by the presence of a sufficient amount of neoplastic cells. The aim of this work is trying to optimize the tissue taken by lymph node biopsy in a patient with suspected extra-medullary lymphoma, producing cell cultures added with a specific combination of B-cell mitogen named DSP30 with Interleukin 2, the same used in the BM cultures. On this "enriched" and correctly processed sample, we performed a complete analysis of the karyotype that, in some cases, allowed to identify additional chromosomal alterations comparing to those highlighted by FISH analysis. Based on the obtained results, we believe that we have developed an ideal protocol to improve the cytogenetic analysis of lymphomas, including the different types of cell culture, the use of an appropriate mitogen and the analyses made by conventional and molecular cytogenetics. Our methodological approach, moreover, allows storing cells suspension, bioptical and histological samples, that can be used also later to perform molecular genetic investigations.