The authors show the clinical and histopathological difficulties for the diagnosis of a rare ovarian tumor in a 13 year old girl who had a bone disease called enchondromatosis, and the adequate treatment for this case. Laparotomy was performed with unilateral salpingo-oophorectomy of the left ovary after a detailed study to detect the origin of the pelvic mass, the patient, who had metrorrhagia and pains in the lower abdomen. Three years after surgery, the patient was once again seen in the outpatient clinic with regular catamenia, requesting some oral contraceptives because she had started sexual activity. The authors conclude that the lipid cell tumor of the ovary is difficult to classify and diagnose, and that it is normally benign, and that treatment for this type of tumor, specially in youngsters, in whom one should be concerned with maintaining menstrual and reproductive function, is the unilateral oophorectomy.