Context: Diagnosis of extraovarian fibrotic disease during surgical procedure in an asymptomatic patient. Objective: To report a case of extraovarian fibrothecoma in a pregnant patient, discovered only at the moment of fetal extraction. Methods: Case report. Patient (s): M. H. A., 37 years old, gravida 3, para 2, 39 weeks and 2 days, previously healthy, was admitted to Mae Esperanca Municipal Birth Center with severe lower abdominal pain with onset 24 hours earlier. Due to the history of two previous cesarean sections, surgical intervention was performed to remove the fetus. After removal of the fetus, an adnexal mass of approximately 5 cm was seen in intimate contact with the left ovary, with a hardened appearance and smooth surface, yellowish-white colored and multiple prominent vascular structures. Intervention(s): Due to the aspect of the adnexal mass, the left ooferectomy was performed, with subsequent anatomopathological analysis showing fusiform cell neoplasia permeated by accumulation of free droplets and foamy macrophages without pleomorphism or observable mitoses. Main Outcome Measure (s): None. Result (s): The patient progressed steadily and was discharged 48 hours after the surgical approach. Conclusions: The present case corresponds to a process of benign biological behavior, which makes it infrequent. In this case, the diagnosis was only possible during the surgical procedure due to the pregnancy cycle. From the case reported, the knowledge of this entity is considered fundamental, which may suggest ovarian neoplasia during the surgical evaluation.