Fibroma and inflammatory myofibroblastic tumor of the heart.

Cardiac fibroma and inflammatory myofibroblastic tumor (IMT) of the heart are rare lesions occurring in young patients and having pathologic similarities. We compared the morphologic and immunohistochemical features of seven cardiac fibromas, including one biopsied at birth and removed 4 years later, and two IMTs of the heart diagnosed at Marie Lannelongue Surgical Center (Le Plessis Robinson, France) between 1980 and 1999. Cardiac fibromas occurred in five females and two males and were surgically biopsied (n = 2) or removed (n = 6) between the ages of 8 days to 31 years (mean 7 +/- 12 years). Inflammatory myofibroblastic tumors were removed in two male patients, aged 13 weeks and 1 year, both alive and well 9 months and 5 years after surgery, respectively. Fibromas were ventricular lesions measuring 3 to 10 cm (mean, 5.7 +/- 2.2 cm). They contained entrapped myocytes and wavy elastic fibers. Three cases contained calcifications. Spindle cells were monomorphic. Their nucleus had a thin chromatin without nucleolus. Mitoses and extramedullary hematopoiesis were only observed in fibromas from patients younger than 5 months (n = 5) while prominent collagen fibrosis was present in fibromas from patients older than 4 years (n = 3). Inflammatory myofibroblastic tumors were endocardial lesions measuring 2 and 2.5 cm. They were covered by fibrin. Spindle cells were larger than in fibromas. Their nucleus had obvious nucleoli. They were associated with numerous inflammatory cells in a variable amount of myxoid background. Occasional mitoses and foci of necrosis were present. Spindle cells in both fibromas and IMTs strongly expressed smooth-muscle actin and were negative for desmin, CD34, S-100 protein, and p53. Our study shows that IMT must be considered in the differential diagnosis of cardiac fibroma especially in cases of inflammatory syndrome, location outside the ventricular myocardium, or multinodular lesions. Morphologic analysis permits the correct diagnosis, while immunochemistry shows a myofibroblastic differentiation in both lesions. Copyright 2001 by W.B. Saunders Company