Deep fbromatosis of desmoid type comprises rare mesenchymal tumors characterized histologically by proliferation of fbroblasts and myofbroblasts. These lesions are characterized by infltrative growth and local recurrence but an inability to metastasize. They can be located in the abdominal wall (generally in sutures), intra or extraabdominal. The best imaging modality for evaluation and staging of the deep fbromatoses is MR imaging. These well or ill-defned lesions generally present internal hypointense bands, with lack of enhancement in post contrast images (collagen bundles) and are usually centered in an intermuscular location with a rim of fat (“split fat sign”), although invasion of surrounding muscle is frequent. Linear extension along fascial planes (“fascial tail sign”) is also a frequent manifestation in deep fbromatoses and is uncommon with other softtissue neoplasms. MR image signal intensity has an implication on tumor recurrence, with a higher recurrence rate in lesions with high T2 signal. In surgically untreated lesions, with undergoing radiation or drug therapy, MR surveillance has been used to assess response to treatment with positive results demonstrating decrease in T2 signal, lesion enhancement and lesion size.

Keywords: Aggressive fbromatosis; desmoid tumor.

The evaluation of sonographically indeterminate adnexal lesions should be performed with MRI (Magnetic Resonance Imaging). It is fundamental to determine the exact location of the lesion, since the differential diagnosis and therapeutic approach are distinct according to the organ of origin. Some signs that may indicate an ovarian origin are: the presence of ovarian follicles and normal ovarian parenchyma surrounding the lesion, without a cleavage plane (“embedded organ sign”); a change in the ovarian contour by the mass (“beak sign”); visualisation of a vascular pedicle or the gonadic veins leading to the lesion (“suspensory ligament sign”); deviation of the iliac vessels laterally and of the pelvic ureters posteriorly or postero-laterally. The majority of ovarian lesions show cystic components with high signal-intensity on T2 weighted-imaging. Hypointense lesions on T2 are less frequent. The differential diagnosis for T2 hypointense ovarian lesions can be vast: haemorrhagic lesions (namely endometrioma); presence of smooth muscle (leiomyoma); presence of fbrous tissue (fbroma, thecoma and cystadenofbroma) and tumours with mixed cellularity (Brenner tumour, “struma ovarii” and Krukenberg tumour).

According to the ESUR recommendations published in 2017, diffusion-weighted imaging (DWI) should be applied for those lesions, using high b-values. The lesions that show lowsignal intensity on DWI are classifed as benign and do not require further investigation. On the other hand, for lesions that demonstrate intermediate or high signal on DWI, it is essential to administrate intravascular contrast, ideally with dynamic-contrast enhanced imaging (DCE).

Keywords: T2-hypointense lesions; Ovarian lesions; MR; Haemorrhagic lesions; Fibrous tissue; Mixedcellularity tumours.