Nodular pulmonary amyloidosis, a rare localized form of amyloidosis, has been associated with immunoglobulin light chains (AL type) and variably with low-grade lymphoma. The clinicopathologic features of 18 cases were investigated; 5 of 14 had autoimmune disease. In 14 cases monotypic plasma cells could be demonstrated by immunohistochemistry. By mass spectrometry analysis of the amyloid deposits, all 18 cases showed a peptide profile with an abundance of immunoglobulin light chains (12 κ, 4 λ, and 2 mixed κ and λ), with 13 also showing significant codeposition of heavy chains (10 γ, 2 α, 1 δ). Of 14 patients with follow-up, 3 developed recurrent pulmonary amyloidoma, 2 had pulmonary recurrence plus cutaneous extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) type with and without amyloid, and 1 had a history of parotid gland MALT lymphoma. This study highlights the unique features of this localized form of amyloidosis. AL κ type is more frequent than AL λ type, with a ratio of 3:1, in contrast to the AL λ predominance that characterizes systemic AL amyloidosis. In addition, the majority of nodular pulmonary amyloid is of mixed AL/AH type, a rare finding in systemic amyloidosis. The association of nodular pulmonary amyloidoma with autoimmune disease and lymphoma indicate the majority of these lesions relate to an underlying lymphoplasmacytic neoplasm in the spectrum of MALT lymphoma.