[Primary breast lymphoma]

A 66-year-old woman with a previous diagnosis of benign histiocytosis of the right breast developed intermediate grade malignant lymphoma of her left breast 6 years later. It is suggested that the primary disease was actually a low-grade lymphoma of the MALT subgroup (mucosa-associated lymphoid tumors) which 6 years later had undergone transformation into high-grade lymphoma. This assumption is based on the known histological similarity between MALT lymphomas and benign histiocytosis.