A Case of Infantile Digital Fibromatosis

ABSTRACT

We report a case of infantile digital fibromatosis in a 34 month-old boy, who presented with a painless subcutaneous tumor on the medial aspect of the left third toe. A histological examination showed scattered small, round eosinophilic inclusion bodies in the cytoplasm of the tumor cells, which was consistent with infantile digital fibromatosis. A'immunohistochemical study revealed that desmin, a-smooth muscle actin, and vimentin were clearly positive in the cytoplasm of the tumor cells, but the inclusions themselves showed negative staining, thus indicating a hollow-like staining pattern. Electron microscopy showed either well-defined or ill-demarcated dense bodies in the cytoplasm of the tumor cells. In some areas, small vesicles and intracellular organells were observed' in the inclusions. In the course of conservative treatment, a new lesion developed on the lateral aspect of the left third toe, seven months after the appearance of the initial lesion.