Primary pulmonary MALT lymphomas show frequent and heterogeneous cytogenetic abnormalities, including aneuploidy and translocations involving API2 and MALT1 and IGH and MALT1.

Divisions of Anatomic Pathology and Hematopathology, Mayo Clinic, Rochester, MN 55905, USA.

API2-MALT1 fusion and aneuploidy are common chromosomal abnormalities in MALT lymphoma. In studying their incidence and relationship in primary pulmonary MALT lymphomas, a translocation involving MALT1 and IGH was also identified. In all, 28 primary pulmonary MALT lymphomas were studied by fluorescence in situ hybridization using an API2-MALT1 probe and multiple centromeric probes, as well as IGH-BCL2, IGH-MALT1, and MALT1 breakapart probes in selected cases. Seven (25%) had API2-MALT1 fusion; all seven lacked aneuploidy except for two with trisomy 3 in a small clone. Three (11%) had IGH-MALT1 fusion; two also showed trisomy 3 and 12. A total of 11 (39%) had aneuploidy only, with trisomy 3 and 18 being the most common. Ectopic nuclear bcl-10 expression, which has been previously associated with API2-MALT1, was seen by immunohistochemistry in 86% of API2-MALT1 fusion-positive cases, one IGH-MALT1 fusion-positive case, two aneuploidy-only cases, and two normal cases. In primary pulmonary MALT lymphomas, cytogenetic abnormalities are common (75%) and heterogeneous, encompassing API2-MALT1 and IGH-MALT1, which are mutually exclusive, as well as aneuploidy, which may be present in the latter but is rare in the former. Ectopic nuclear bcl-10 expression is associated with API2-MALT1 but may also be seen in IGH-MALT1 fusion-positive, aneuploidy-only, and normal cases.

PMID: 14574335 [PubMed - indexed for MEDLINE]