Does MALT lymphoma of the lung require immediate treatment? An analysis of 11 untreated cases with long-term follow-up.

BACKGROUND Mucosa-associated lymphoid tissue lymphoma (MALT lymphoma) of the lung is a relatively rare disease. As little is known about the natural clinical course if left untreated, all patients undergoing a watch-and-wait policy at our institution were investigated. PATIENTS AND METHODS A retrospective analysis identified a total of 11 patients with MALT lymphoma of the lung who did not undergo treatment following initial diagnosis. All patients had undergone extensive staging and were closely observed with restaging every three months. Histological assessment included immunhistochemistry for demonstration of the immunphenotype CD20+/CD5-/ CD10-/cyclinD1-/CD23-. Genetic aberrations were assessed, using RT-PCR for t(11;18) (q21;21) and fluorescence in situ hybridisation for the evaluation of t(14;18)(q32;q21), t(1;14) (p22;q32), trisomies 3 and 18. RESULTS Five patients had MALT lymphoma restricted to the lung, while the remaining six had additional extrapulmonary sites detected during staging. The median time of observation without therapy was 28.1 months (inter-quartile range: 5 to 60 months); within this time, all 11 patients showed at least stable disease. Six of these 11 patients, however, had spontaneous regressions and wax-and-wane phenomena of the pulmonary lesions, but not of extrapulmonary manifestations. Three of these patients had evidence of t(11;18)(q21;q21), while the remaining three had no evidence of genetic aberrations. One patient was referred for treatment after progression in the lung, while two patients experienced progression outside the lung. Currently, all patients are alive, with 8 patients still only being watched. CONCLUSION Our findings suggest that MALT lymphoma of the lung is a very indolent disease with the potential for spontaneous regression. In view of this, patients diagnosed with pulmonary MALT lymphoma might not require immediate treatment in the absence of symptoms and a watch-and-wait policy could be adopted.