Amyloid deposition in primary pulmonary marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue.

A rare association between primary pulmonary marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), and pulmonary immunoglobulin light chain (AL) amyloidosis is described in a 65-year-old woman suffering from rheumatoid arthritis (RA). All four nodules in the resected upper lobe of the lung had a similar histological appearance. They were composed of small-medium-sized atypical lymphocytes. Centrocyte-like cells had lymphoepithelial lesions. Immunohistochemically, the tumor cells clonally expressed B-cell markers, and demonstrated clonal rearrangement of the immunoglobulin heavy chain gene on polymerase chain reaction. Based on these findings the diagnosis of primary pulmonary MALT lymphoma was made. In addition, uniform eosinophilic material deposition was identified randomly within the tumor. It was Congophilic and exhibited apple-green birefringence on polarizing microscopy, and remained unaffected by potassium permanganate digestion. Deposited material was immunoreactive to lambda light chain. It was concluded that this material was AL amyloid in primary pulmonary MALT lymphoma. Plasma cells with mRNA of lambda chain was found infiltrated along the border of amyloid deposition. Finally, it is speculated that primary pulmonary MALT lymphoma developing in an autoimmune setting, RA in the present case, is associated with overproduction and abnormal clearance of immunoglobulin by the tumor cells, resulting in AL amyloidosis within the tumor.