Pulmonary mucosa-associated lymphoid tissue lymphoma associated with pulmonary sarcoidosis: a case report and literature review.

Differentiating low-grade lymphoma from preexisting sarcoidosis is difficult because of their pathological similarity. This article describes a case of pulmonary mucosa-associated lymphoid tissue lymphoma associated with pulmonary sarcoidosis. The patient, a 45-year-old Japanese man, presented with a 10-year history of pulmonary sarcoidosis and 5-year history of ocular sarcoidosis with histologic findings. Because only the right S3 lung nodule had gradually enlarged, partial resection was performed. Pathological study revealed noncaseous epithelioid granulomas with lymphoplasmacytic proliferation but also marked lymphoid cell proliferation with lymphoepithelial lesion findings that differed from findings of typical sarcoid lesions. Our lymphoepithelial lesion evaluation via immunohistochemistry and analysis of Ig heavy-chain gene rearrangements with assessment of Propionibacterium acnes-specific antibody reactions allow us to report, for the first time, this case of pulmonary mucosa-associated lymphoid tissue lymphoma associated with pulmonary sarcoidosis in exactly the same location, which may be significant for differentiating these diseases and understanding their pathogenic association.