OBJECTIVE: To tell to a case of fibromatosis type desmoids causing peripheral easy paralysis. STORY OF THE CASE: Patient, masculine, 6 months of age, with mass to retroauricular inferior hard left approximately measuring 4,0 X 2,5cm. To the RNM examination, situated injury of expansive aspect in soft parts below of the left mastoid, in region predominantly to retroauricular and without intracranial alterations was observed. After 03 months, the patient evolved with face paralysis peripheral left. New examination of RNM showed increase of the dimensions of the injury. In this already showed to contact of the mass with mastoid and the superior edge of the sternocleidomastoid muscle, but without intracranial alterations. TC of mastoids showed solid mass to retroauricular left compatible with RNM. Mastoids and average box bilaterally without alterations. The patient was submitted to the surgery and the part was ordered for the histopathological that disclosed: fibromatosis type desmoids involving gland to salivary. The result of the immunohistochemistry was: compatible morphologic picture and immunohistochemistry profile with miofibromatosis. It is presented until the moment without return (control for RNM). CONCLUSION: To rare tell to a place of tumor desmoids and an atypical manifestation of this. We must, then, extend the diagnostic hypotheses in young patients with symptomatology of tumor to retroauricular and face paralysis peripheral ipsilateral.