Marginal Zone B-cell Lymphoma Arising from Buccal Mucosa Resembling Inflammatory Myofibroblastic Tumor of the Soft Tissue

We report here a case of marginal zone B-cell lymphoma (MZBL) arising from buccal mucosa resembling inflammatory myofibroblastic tumor (IMT) of the soft tissue. On a low-power field, the lesion is characterized by fibrous granulation tissue and numerous lymphoid follicles with or without atrophic small germinal center. A portion of the lymphoid follicles were surrounded by partial and/or complete thin pale cuff of centrocyte-like (CCL) cells on high power field. The thin rim of the lymphoid follicles contained CCL-cells, plasma cells, cells showing plasma cell differentiation and mature eosinophils. In contrast, the granulomatous areas contained were characterized by haphazardly arranged spindle cells, mature plasma cells, mature eosinophils, small-to-medium lymphocytes and histiocytes. Histologically, IMT was suspected. However, flow cytometry and immunohistochemical study demonstrated a monotypic nature of centrocyte-like cells, plasma cells and their precursor and confirmed the diagnosis of MZBL arising from the buccal mucosa. The differential diagnostic problems between IMT of the soft tissue and classical Hodgkin lymphoma and T-cell lymphoma have been discussed previously. However, the present case indicated that MZBL should be added to the differential diagnosis of IMT of the soft tissue.