[Primary ocular adnexal lymphoproliferative lesions: clinicopathologic features and genetic alterations]

To investigate clinicopathological and genetic characteristics of primary ocular adnexal lymphoproliferative lesions.

Clinical, morphological and immunohistochemical features of 37 archival cases of primary ocular adnexal lymphoproliferative lesions were studied including 5 cases of reactive lymphoid hyperplasia and 32 lymphomas retrospectively. Classification of the lymphomas were made according to the WHO classification of tumors of haematopoietic and lymphoid tissues. All cases were studied by interphase fluorescence in situ hybridization (FISH) using dual color break apart probes of IgH, MALT1, bcl-6, c-Myc, bcl-2, CCND1, bcl-10, and FOXP1 for detection of chromosomal aberrations involving IgH, MALT1, bcl-6, c-Myc, bcl-2, cyclinD1, bcl-10 and FOXP1 genes, respectively. FISH with IgH / bcl-2 dual color dual fusion probe was used for detection of t(14;18)(q32;q21)/IgH-bcl-2. CEP18 spectrum orange probe was used for detection of aneuploidy of the chromosome 18.

Among 32 cases of lymphomas, 28 cases (87.5%) were extranodal marginal zone B-cell lymphomas of mucosa associated lymphoid tissue (MALT lymphoma), 2 cases were follicular lymphoma (FL) and 2 cases diffuse large B cell lymphoma (DLBCL). Among the 28 cases of MALT lymphoma, chromosomal aberrations were found in 60.7% (17/28) by interphase FISH analysis. One case showed positive IgH break-apart signal with unknown partner. 16 cases showed three copies of different genes, of which, three copies of MALT1, bcl-6, and c-Myc were identified in 7 cases (25%), 12 cases (43%), and 2 cases (8%) of MALT lymphomas, respectively. In addition, 5 cases showed two genes including three copies of bcl-6 and MALT1 in 4 cases, and three copies of bcl-6 together with c-Myc in one case. Furthermore, all cases with three copies of MALT1 had trisomy 18. t(14;18)(q32;q21) was detected in both follicular lymphomas. Of the 2 DLBCL cases, one showed three copies of bcl-6 together with trisomy 18 and the other one showed three copies of bcl-6 together with IgH and c-Myc rearrangements. Chromosomal aberration was not found in all 5 cases of reactive lymphoid hyperplasia.

The most common entity of primary ocular adnexal lymphomas is MALT lymphoma and FISH is helpful for their differential diagnosis and classification. Trisomy 18 and three copies of bcl-6 are common chromosomal aberrations in primary ocular adnexal MALT lymphomas.