Inflammatory pseudotumor of the submandibular gland - Report of a case presenting with autoimmune disease-like clinical manifestations

We report a rare case of inflammatory pseudotumor arising in the submandibu lar gland, which presented with autoimmune disease-like clinical manifestat ions. A 70-year-old Japanese man developed masses in both submandibular reg ions. Laboratory tests revealed polyclonal hypergammaglobulinemia, high tit ers of antinuclear antibody, and a positive thyroid test. Histologically, t he lesion was composed of multiple nodules separated by thick fibrous bands and contained a few atrophic lymphoid follicles and residual ductal struct ures. At higher magnification, the nodules contained numerous mature plasma cells mixed with myofibroblasts, lymphocytes, and histiocytes. Occasionall y, the myofibroblasts were arranged in poorly formed fascicles and in a sto riform pattern. Polymerase chain reaction analysis failed to demonstrated t he rearrangement of the immunoglobulin heavy-chain gene. The patient was fr ee of disease after 72 months follow-up. Marginal zone B-cell lymphoma of m ucosa-associated lymphoid tissue (MALT) type arising from salivary glands o ccasionally showed prominent plasma cell differentiation. The present case indicates that inflammatory pseudotumor should be added to the list of diff erent diagnoses for mucosa-associated lymphoid tissue-type lymphoma of the salivary glands.