Primary Non-Hodgkin’s Lymphoma of the Lung.

Background: Unlike the relatively common secondary involvement of the lung in patients with widespread disease, primary lung lymphoma (PLL) is a rare disease with a few reports in the literature and information based mainly from small series of patients. We conducted a study in a large population database to improve the current knowledge of this malignancy.

Methods: The SEER database was searched for primary non-Hodgkin’s lymphoma (NHL) of the lung in patients aged 20 or older and diagnosed between 1988 and 2003. Entry criteria included lung malignancies with codes for histology 9670–9699 (mature B-cell lymphomas), 9700–9719 (mature T and NK-cell lymphomas), 9720–9729 (precursor cell lymphoblastic lymphomas) and NHL at primary sites labeled C34.0 (main bronchus), C34.1 (upper lobe), C34.2 (middle lobe), C34.3 (lower lobe), C34.8 (overlapping), and C34.9 (lung NOS). All primary lung NHLs (also including histology codes 9590–9599, malignant lymphoma, NOS or diffuse) were used in the calculation as a percentage of total NHLs and primary lung tumors, but only patients with known histology were used for further analysis.

Results: There were 1,652 cases of PLL, which accounted for 5.2% of all extranodal NHL and 1.7% of all NHL. PLL represented 0.4% of all primary lung cancers, but 51% of non-carcinoma histologies. Among the PLL cases, 355 did not have histological definition, leaving 1,297 eligible for further analysis. The median age at diagnosis was 65 years, and the disease was slightly more common in males (53.2% male; male/female ratio of 1.14). Most of the patients were Caucasians (85.6%), and the most common histologies were diffuse large B-cell (DLBCL) (51%), marginal zone B-cell lymphoma (MZL) (25.2%), small lymphocytic lymphoma (SLL) (9.2%), and follicular lymphoma (FL) (5.3%). Stage distribution was as follows: stage IE - 45.2%, stage IIE - 18.1%, stage IIIE/IIIES - 2.7%, and stage IV - 34.0%. Most patients presented with early-stage (IE/IIE) disease (63.3%). Surgery and radiation were the initial therapy in 36.2% and 13.1% of the patients respectively. Median overall survival was 58 months, and 5-year survival was 48.5%. The 5-year survival rates for patients with early stage disease (IE and IIE) according to histology were as follows: DLBCL - 36%, MZL - 78%, SLL - 71%, and FL - 81%.

Conclusions: PLL is a rare disease with limited information from the literature. Although it accounts for a small fraction of both NHLs and primary lung tumors, it is the most common pulmonary malignancy of non-carcinoma histology. It occurs most commonly in elderly patients, with a slight male predominance. Nearly two-thirds of the patients present with early-stage disease, and approximately half of the patients are alive at 5 years.