Arguably the MYC activity gain is the most constantly observed phenomenon (>70% of cases) in transformed FL/MALT/CLL (Richter's transformation) and co-occurs with specific aberrations such as the loss of p53, CDKN2A/B, or gain of BCL2/BCL6.
The most common scenario is transformation of follicular lymphoma to either diffuse large B-cell lymphoma or high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 translocations; however, other indolent subtypes such as marginal zone lymphoma, lymphoplasmacytic lymphoma, small lymphocytic lymphoma/chronic lymphocytic leukemia, or even nodular lymphocyte predominant Hodgkin lymphoma, can undergo similar histologic transformation.
Fluorescent in situ hybridization detected IGH/BCL2 translocation in 1 FL, increased BCL6 copy number in another FL, BCL6 rearrangement, and increased copy number of MYC and MALT1 in the DLBCL with marginal zone lymphoma.
In the current study, C-MYC expression was detected in MALT lymphomas, and its relationship to the occurrence of LTCs, clinicopathological parameters and prognosis was assessed.
Translocations involving IGH were detected in 36 (32%) of 111 cases; their partner genes included BCL6 (n = 10), c-MYC (n = 5), and FOXP1 (n = 3) but remained unknown in the remaining 18 cases. t(14;18)/IGH-BCL2, t(14;18)/IGH-MALT1, and t(1;14)/BCL10-IGH were not detected in any case. t(11;18)/API2-MALT1 was detected in none of the cases, except for one case of DLBCL with MALT lymphoma, which showed positive signals only in MALT lymphoma cells.
To further investigate whether ASHM also occurs in mucosa-associated lymphoid tissue type (MALT) lymphoma, we studied the mutation profile of PIM1, PAX5, RhoH/TTF, and c-MYC in 17 MALT lymphomas and 17 extranodal diffuse large B-cell lymphomas (DLBCLs) still exhibiting a low-grade MALT lymphoma component (transformed MALT lymphoma).
Mutation in exon 2 of the c-myc gene was present in 2 of 20 (10%) patients with low-grade MALT lymphoma, in 1 of 7 (14%) patients with high-grade MALT lymphoma, and none of 10 patients with DLL.
Twenty-seven lymphomas of mucosa-associated lymphoid tissue (MALT) derived from distinct anatomical sites were tested for the presence of genetic lesions commonly involved in B-cell lymphomagenesis, including activation of proto-oncogenes (BCL-1, BCL-2, BCL-6, and c-MYC), disruption of tumor suppressor loci (p53, 6q), and infection by viruses [Epstein-Barr virus (EBV), and Kaposi's sarcoma-herpesvirus/human herpesvirus-8 (KSHV/HHV-8)].