Inflammatory pseudotumor (inflammatory myofibroblastic tumor) of the mitral valve of the heart.

We report a rare case of inflammatory pseudotumor/inflammatory myofibroblastic tumor (IPT/IMT) of the heart, involving the mitral valve. A 58-year-old woman presenting with dyspnea was immediately admitted to the hospital, and found to have congestive heart failure due to the invagination of a tumor-like mass of the mitral valve. This mass arose from and involved almost the entire posterior leaflet of the mitral valve and occupied almost the entire mitral valve orifice. The tumor was a yellowish-white well-circumscribed mass with a smooth surface. The excised mass was 3.0 x 2.3 x 1.8 cm, and consisted of abundant Sudan III-positive foam cells, histiocytes, lymphocytes, plasma cells, and loosely arrayed spindle cells, in vascular-rich fibrous tissue. Immunohistochemistry showed that the spindle cells were positive for vimentin and alpha-smooth muscle actin, and negative for desmin, CD34, and human muscle actin (HHF-35), suggesting they were myofibroblastic cells. The plasma cells and lymphocytes showed no monoclonality. There were few mitotic cells, and, except for the lymphocytes, few Ki-67-positive cells. The findings suggested IPT/IMT. The 39 cardiac IPT/IMT cases appearing in the English-language literature are discussed.