RESUMO
BACKGROUND: Desmoid tumor is a rare benign mesenchymal neoplasm in children primarily originated in the muscle connective tissue, fascial sheaths, and musculoaponeurotic structures. It is often misdiagnosed as fibroids, reactive processes or low-grade fibrosarcomas. It is characterized by slow growth, locally aggressive nature, high recurrence rate without metastasize capacity. MATERIAL AND METHODS: 7 year old girl with right paramandibular tumor, a year of evolution. It was characterized by slow and painless growth, trismus and mandibular latero-deviation to the left during mouth opening. Imaging tests showed soft parts tumor in masseteric region with a periosteal reaction in the mandibular body. The biopsy reported a desmoid tumor. RESULTS: Risdon approach was performed for tumor resection and external cortical Split mandibular body, without preserving the marginal branch of CP VII. The pathology reports of aggressive fibromatosis without bone involvement. It currently presents marginal paralysis and free-disease. CONCLUSIONS: Desmoid tumors of head and neck are difficult to treat because of the proximity or involvement in vital structures, infiltrative nature and tendency to local recurrence. Primary surgery with negative surgical margins is the treatment of choice. However, in many cases this involves disfiguring surgery. Therefore, in these cases and in those surgical margins affections, the use of chemotherapy/non-cytotoxic drugs can be an alternative. Because they are low incidence tumors prospective multicenter studies are needed to clarify the role of adjuvant treatment in this tumor.