Primary Malignant Lymphoma of the Lung (Low-grade B-cell Lymphoma of MALT Type) Occurring in a Patient with Bronchiolitis Obliterans Organizing Pneumonia

In May 1986, a 71-year-old woman was found by chest X-ray to have a nodular shadow in the right middle lobe, which later disappeared spontaneously. In June 1990, her chest X-ray showed wandering shadows diagnosed as bronchiolitis obliterans organizing pneumonia (BOOP) by trans-bronchial lung biopsy (TBLB); this was resolved by October 1990 without steroid therapy. During the follow-up period a nodular shadow of the right upper lobe appeared in December 1994, and gradually enlarged. To determine the diagnosis, a right upper lobectomy was performed in May 1995. Histological examination revealed low-grade B-cell lymphoma of the MALT type. Among defects of autoimmune disorders including Sjogren's syndrome, B-cell activation in BOOP was suspected to be inducing B-cell lymphoma in this case