**5.6 Malignant transformation in endometriosis**

Malignant transformation in endometrioma is a rare well-known complication of endometriosis, occurring in a younger age group with estimated incidence is less than 1% of women with ovarian endometriosis. The common histologic types are endometrioid adenocarcinoma and clear cell carcinoma arising from glandular elements and rare form is endometrial stromal sarcoma occurs arising from stromal elements. Loss of the T2 shading effect is more commonly detected in malignant than in benign endometriomas. The postulated reasoning for this is dilution of haemorrhagic fluid by tumor secretions, although is not specific to malignant endometrial cysts. Enhancing mural nodules within a cystic mass is another feature of malignant change in endometriosis. Typically mural nodules are enhancing, T1-weighted low and variable T2-weighted signal intensities. Dynamic subtraction images with a gradient- echo sequence often improve nodule enhancement. Again, enhancing mural nodules within endometriotic cysts, although seen more commonly in malignant endometriomas is not specific and has been reported in benign lesions.

## **5.7 Scar endometriosis**

444 Endometriosis - Basic Concepts and Current Research Trends

effect of degenerated blood products present at different stage within the same cyst. It can

Since both the haemorrhagic cysts and the chocolate cyst contain blood products, it can be difficult to distinguish between them except for the fact that hemorrhagic cysts do not display shading, are mostly unilocular and resolve on interval imaging. In contrast dermoid cysts are easily diagnosed on MRI since they lose the signals and become dark on fat

After contrast administration, the periovarian peritoneal surface of the cyst can be enhanced which can help in identification of torsion ovary. Endometrioma in an enlarged but poorly enhancing ovary with peripherally located follicles is suggestive of torsion ovary on

Solid deep lesions display low to intermediate signal intensity with punctuate areas of high signal intensity on T1 weighted images. Uniform low signal intensity is seen on T2 weighted images. The punctuate foci of high intensity are due to the zone of haemorrhage surrounded by abundant solid fibrous tissues. These may actually mimic metastatic lesions arising from intraperitoneal malignancies such as ovarian carcinomas. The two entities can be differentiated on T2 weighted images by the low signal intensity imparted by solid

Masses situated in the pouch of Douglas, posterior vaginal fornix and uterosacral ligaments may comprise of large fraction of glandular material with little fibrotic reaction, imparting hyperintense signals on T2 weighted images. Administration of contrast material will enhance such solid lesions, making it possible to distinguish it from necrosis or intramural hemorrhage. Frequently the signal intensity may not be able to pick up the deep endometriosis of the uterosacral ligaments, especially if the punctuate foci of haemorrhage are missing in the lesion. In such case, the diagnosis is often made by correlating the thickening of the ligaments. Thickening more than 9mm in size or nodularity within the ligaments either

Bladder endometriosis can be identified on MRI by deviation in signal intensity and gross anatomical anomalies in bladder wall thickness which can be localized or diffuse. Most of the times there are foci of high signal intensity in abnormally thickened bladder wall. Such findings may exist even if patients have normal cystoscopy result or without urinary symptoms. Bladder endometriosis infact infrequently infilterates the mucosa. Thus it is difficult to make out the lesions on cystoscopy. Advanced disease may present as ureteral

Deep rectal involvement is less obvious on MRimaging due to the rectal contents which impart artifacts. Conventional MRI has infact sensitivity of only 33%. Results can be

endometriomas often in combination with the presence of endometrial cyst.

bilateral or asymmetrical often give clue to the diagnosis.

range from subtle layering to a complete signal void (black).

suppressed sequences.

**5.3 Solid deep lesions** 

**5.4 Bladder endometriosis** 

obstruction and hydronephrosis.

**5.5 Rectal endometriosis** 

MRimaging.

Solid endometriosis can also develop in a caesarian section scar. MRI is valuable in identifying these lesions. MRI characteristically shows high signal intensity on T1 and hypointensity on T2 weighted images. Fat saturated sequences are more helpful in the diagnosis specially in context of myometrium along the surgical scar.
