Mucosa-associated lymphoid tissue (MALT) lymphoma is a type of an extranodal marginal zone B-cell lymphoma that accounts for about 5% to 8% of all B-cell lymphomas. It is rare for a recurrent oral MALT lymphoma to have tetraploidy with a double t(11;18) chromosomal abnormality, however.
A 66-year-old Japanese woman with a swelling of the right buccal mucosa was referred to our hospital. A tumor was excised, and a pathologic diagnosis of MALT lymphoma with a t(11;18) (q21; q21) chromosome translocation was made. Two years later, swelling of the right buccal mucosa recurred, which was then excised and pathologically diagnosed as MALT lymphoma. This tumor did not have a t(11;18) (q21; q21) chromosome translocation, but exhibited tetraploidy with double t(11;18).
FISH analysis revealed that the recurrent MALT lymphoma of the buccal mucosa had tetraploidy with double t(11;18). This is the first reported case of a recurrent MALT lymphoma showing tetraploidy with double t(11;18).