A rare case of synchronous mucosa-associated lymphoid tissue (MALT) lymphoma involving bilateral breasts and subcutaneous tissues.

Marginal zone lymphoma of mucosa-associated lymphoid tissue is a B-cell lymphoma which arises in extranodal sites, most commonly the stomach. Involvement of the breast is very rare. We present a case of an asymptomatic 63-year-old woman with synchronous mucosa-associated lymphoid tissue lymphoma involving both breasts and subcutaneous tissues. This represents a form of secondary breast lymphoma (given the concurrent involvement of the breast and non-mammary organ systems) and is an exceedingly rare diagnosis which, to our knowledge, has only been discussed in a few case series.