Congenital dermatofibrosarcoma protuberans in a newborn infant with a massive back tumor: favorable effects of oral imatinib on the control of residual tumor growth.

Dermatofibrosarcoma protuberans (DFSP) is known as a very rare malignant tumor of the deep dermis and subcutaneous tissue. It typically develops during adolescence and adulthood, with pediatric and infantile cases, particularly congenital ones, being much less frequent. We report a neonate with congenital DFSP. A newborn girl presented with a massive back tumor at birth. The tumor was at first suspected to be infantile fibrosarcoma (IFS) after immunohistochemical analysis of biopsy material, although the results were not fully compatible with IFS. She received chemotherapy under a tentative diagnosis of IFS, but this was unsuccessful. Partial resection was therefore performed at the age of 8 months to reduce the tumor mass and to reexamine its immunohistochemical characteristics. Positive CD34 staining and Collagen α1α/platelet-derived growth factor beta chimera gene signals on analysis of the excised tumor tissues enabled a definitive diagnosis of DFSP. She then underwent local irradiation and was given a daily dose of oral tyrosine kinase inhibitor (imatinib). After almost 1 year, the patient is doing well without enlargement of the residual tumor.