Pulmonary crystal-storing histiocytosis and extranodal marginal zone B-cell lymphoma associated with a fibroleiomyomatous hamartoma.

Crystal-storing histiocytosis (CSH) is a rare disorder occurring in patients with lymphoproliferative diseases, predominantly in cases of multiple myeloma and low-grade B-cell lymphoma. To the best of our knowledge, only three cases of pulmonary CSH have been reported in the English literature and one of them was associated with a low-grade B-cell lymphoma (immunocytoma). We document a case of a 59-year-old man with bilateral lung masses in which a right middle lobe pulmonary lobectomy specimen showed CSH associated with an extranodal marginal-zone B-cell lymphoma. A single nodule showing features of fibroleiomyomatous hamartoma was present in a wedge biopsy specimen from the left lung. Two nodules within the right middle lobe were composed of sheets of histiocytic cells with abundant eosinophilic cytoplasm resembling striated muscle cells. In addition, there were nodular aggregates and a more diffuse infiltrate of small slightly atypical centrocyte-like lymphocytes, as well as bronchial lymphoepithelial lesions. Immunohistochemistry performed on paraffin-embedded sections demonstrated that the histiocytic cells were immunoreactive with the KP-1 (CD68) antibody while the lymphocytic infiltrate was CD20 positive, co-expressed for CD43, and was negative for CD3, CD5, and CD10. Genotypic analysis demonstrated the presence of an immunoglobulin heavy-chain gene rearrangement, indicating the presence of a monoclonal B-cell population. These features were consistent with pulmonary CSH associated with extranodal marginal-zone lymphoma of baltoma type.