[Infantile myofibromatosis. Relationship with the genitourinary tract. Case reports and bibliographic review].

Objective: To present a case of infantile myofibromatosis of visceral location and a review of the literature.

Method/results: We report the case of an 11-year-old Caucasian girl hospitalized for abdominal tumorous mass, weight loss and lack of appetite. Physical examination showed: cutaneous-mucous paleness and a painless, palpable tumorous mass of 8-10cm in the right abdominal flank, of firm consistency with defined edges and extending past the midline. Blood test showed hemoglobin 90 mg/l and erythrocyte sedimentation rate of 130 mm/hour. Chest x-ray and bone study were normal, while abdominal x-ray showed intratumorous calcification, intravenous urographyc showed light displace downwards and outwards of the right kidney. Ultrasound showed a solid echogenic mass with a diameter of 11cm in the right abdominal flank, above and extending towards the lower portion of the right kidney. Surgical treatment for possible neuroblastoma was initiated, during which various tumorous growths were observed in the mesocolon, the largest measuring 7cm, which were removed. Macroscopic examination showed whitish well-defined tumorous growths of firm consistency with focal calcifications. Microscopic examination showed a proliferation of fibroblastic type cells, with some areas having smooth muscle cell characteristics. Diagnosis was myofibromatosis.

Conclusions: Infantile myofibromatosis is the most common fibrous disorder of infancy and childhood, more commonly found between birth and two years of age, may also appear later in life. Etiology is unclear, but certain studies report estrogen involvement in its pathogenesis. Clinical symptoms depend on the location and extension of the lesion and age at presentation. Spontaneous relapse may occur. Prognosis is good in the absence of visceral damage, although generalized congenital myofibromatosis with visceral damage is associated with high mortality especially in the first months of life, due to its destructive capacity, obstruction of vital organs, growth inhibition or infection. Urologic concerns include possible infiltration of genito-urinary organs (kidney, corpus spongiosum) and its association with urologic abnormalities. Ultrastructural and immunohistochemical studies show that the tumor is composed of myofibroblasts, with estrogen receptors, displaying vimentin and smooth muscle actin immunoreactivity. Strict follow up is recommended in patients with congenital myofibromatosis to avoid or detect possible complications that may be life-threatening (Bone survey abdominal-pelvic ultrasound, echocardiogram, chest-abdominal CT and biopsy). The treatment of choice is surgical removal, with extensive excision to avoid possible relapse.