Lymphomas of the breast: pathology and clinical behavior.

Lymphocytes are present in normal breast. A lymphocytic mastopathy characterized by a lymphocytic infiltrate within the breast epithelium has been described, but its relevance as a precursor lesion of mucosa-associated lymphoid tissue (MALT)-type lymphoma of the breast is uncertain. Lymphomas of the breast are uncommon, and a broad variety of histologic types have been reported. The majority are B-cell lymphomas, and the most common type is diffuse large B-cell lymphoma (40% to 70%). MALT-type lymphoma is a distinct subgroup of primary lymphoma of the breast with a reported incidence between 0% and 44% and is characterized by indolent behavior and good prognosis. Burkitt's or Burkitt-like lymphoma can bilaterally involve the breast of a young pregnant or lactating woman and typically behaves aggressively. Primary breast lymphomas behave similarly to lymphomas of similar histologic types and stages presenting at other sites. Treatment of primary breast lymphomas does not include surgery, but is typically based on local radiotherapy, often combined with systemic chemotherapy.