Aggressive congenital fibromatosis of the small intestine in the newborn. Report of a case and review of the literature

A case of so-called congenital fibro(leio)myosarcoma of the small intestine in a 18-day-old female baby, treated only with surgical resection, was stu died by immunohistochemistry and electron microscopy in order to investigat e the proliferating cell type. The tumour cells showed positivity only for vimentin and CD 34 and were negative for smooth muscle actin, desmin, alpha -sarcomeric actin, factor VIIIR: Ag and 5-100 protein. Ultrastructural find ings showed oval nuclei with prominent nucleoli, rare intracytoplasmic mito chondria and well developed rough endoplasmic reticulum. According to histo immunological and electron microscopy findings the proliferating cells were likely to be of fibroblastic origin. A 7-year follow-up showed a favourabl e clinical evolution thus confirming that surgical resection can be a suffi cient therapeutic approach. The morphological findings and clinical behavio ur suggest that more appropriate terminology for this tumour would be "aggr essive congenital fibromatosis" which better highlights its local progressi ve invasion without metastases.