Imprint cytology of low-grade B-cell lymphoma of mucosa-associated lymphoid tissue arising in the thymus: a case report.

Low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) arising in the thymus is a very rare tumor with characteristic morphologic features. We describe a case of thymic low-grade B-cell MALT lymphoma occurring in a 59-yr-old woman with Sjögren's syndrome, in whom the definite diagnosis was difficult at the time of surgery. An immunohistologic and genotypic study, however, was diagnostic of lymphoma. A review of cytologic material was undertaken, and it was felt that the cytologic features in Giemsa-stained preparations in imprint smears were present that initially should have enabled the correct cytodiagnosis and distinction from the other thymic lesions. The findings presented in this study were considered to contribute to the cytodiagnosis of a thymic lesion, which might, in the past, have been erroneously interpreted as another lymphoproliferative disorder.