Infantile myofibromatosis: a light microscopic, histochemical and immunohistochemical study suggesting true smooth muscle differentiation.

Eight cases of infantile myofibromatosis, a rare, sometimes multicentric neoplasm which shows an inherited tendency, have been studied by light microscopy, conventional histochemistry and immunohistochemistry. This tumour is commonest in early infancy and may arise at a wide variety of sites, most often in subcutaneous tissue. Evidence is presented that this entity shows true smooth muscle differentiation, rather than it being of a myofibroblastic nature and hence its current name may be incorrect. In this context, the presence of desmin positivity in six out of eight cases is of particular importance. The differential diagnosis is discussed.